bent (coudées), as in Pagurus; the third joint of their peduncle the longest, and carrying at its extremity two small multiarticulate appendages, which are very short and rather stout, one of which is furnished with many long hairs. External antennæ inserted lower than the preceding, their peduncle bent, and presenting above a small scale, the vestige of a palp. External jaw-feet pediform. The last thoracic ring not anchylosed to the preceding. Anterior feet terminated by a stout, didactylous, wellformed hand: they are of very different sizes. Second and third pairs slender and very long: the two last pairs, on the contrary, short and elevated against the sides of the body, as in the Paguri; the fourth pair are flattened, rather large, and imperfectly didactylous, the immoveable finger of their hand being only formed by a slightly projecting tubercle; the posterior feet, still smaller than the last, are terminated by a small didactylous rather wellformed hand. The abdomen is narrow, elongated, and perfectly symmetrical: the first ring, much narrower than the succeeding ones, has no appendages; the four next segments, on the contrary, each give attachment to one pair of rather large false natatory feet, formed by a cylindrical basilary joint and two terminal blades, one of which is very small and obtuse, and the other large, pointed at the end, and bordered with long ciliary hairs. Caudal fin moderate in size; the middle blade, formed by the seventh abdominal segment, is rounded and ciliated, and the external blades are much longer than the middle ones. (M. E.)

M. Milne Edwards observes that this genus establishes the passage between the Pagurians and Callianassa.

Example, Glaucothoe Peronii, the only species known. Its integuments have little solidity, its carapace is smooth, and its length 8 lines. M. Milne Edwards states that it appears to inhabit the seas of Asia. He is of opinion that Latreille's genus Prophylax approximates closely to Glaucothoe, and ought not perhaps to be distinguished from it: if so Latreille's name has the priority. The latter placed his genus among the Paguri, but after the publication of M. Milne Edwards's Glaucothöe, was uncertain, according to M. Edwards, whether these two generic divisions should not be united.

Callianassa. (Leach.)

See the article: but the student should refer to the accurate and elaborate description and figures of M. Milne Edwards, who records two species:-Callianasse subterranea

and uncinata; and he adds that Callianassa major of Say seems to be distinguished from the two preceding species. Sad Bellini Bro B Axia. (Leach.)

Generic Character-Carapace very much compressed, and terminated anteriorly by a small triangular rostrum. Ocular peduncles very small, cylindrical, and terminated by a hemispherical cornea. Terminal filaments of the internal antennae nearly of the length of the carapace. Peduncle of the external antennae having above a small moveable spine which represents the great lamellar palp observable in the Shrimps. External jaw-feet slender and pediform. Anterior feet compressed, and terminated by a well-formed claw; carpus small. Second pair of feet nearly lamellar, and equally didactylous. The three next pairs monodactylous. Abdomen slightly convex towards the middle, and terminating in a great fin, the five blades of which are nearly of the same length. First ring of the abdomen carrying a rudimentary pair of false feet, and the four succeeding rings provided each with a pair of very well-developed natatory false feet, each composed of a short and stout peduncle, which at its extremity carries a small styliform appendage within, and externally two great oval, very large blades, which are ciliated on the borders. (M. E.)

M. Milne Edwards observes that this genus much resembles Callianassa and Gebia, and he records the only known species, Axia Stirhynchus. Its length is about three inches, and it inhabits the coasts of France and England. at 30

Gebia. (Gebios and Thalassina, Risso; Gebia and to be Upogebia, Leach.) nomolde Generic Character. Carapace terminating anteriorly by a triangular rostrum, and sufficiently large to cover the eyes almost entirely; on each side of its base is a tooth, which is continued with a crest, and forms the lateral border of the upper surface of the stomachal region. Internal antennae very short, but nevertheless their terminal filaments are longer than their peduncle. External antennæ very slender, and presenting at their base no vestige of a moveable scale. External jaw-feet pediform. Anterior feet narrow, terminated by an elongated and imperfectly subcheliform hand: their moveable finger is very large, and in bending downwards its base is applied against the anterior border of the hand, the lower angle of which is prolonged so as to constitute a tooth performing the office of the immoveable finger. The feet next in succession are compressed and monodactyle; the second pair have their penultimate joint large, widened, and ciliated below; the succeeding pairs are more slender. Abdomen long and much narrower at its base than towards its middle, depressed and terminating by a large fin, whose four lateral blades are foliaceous and very wide. First abdominal ring with two pairs of very small filiform appendages; the four next segments giving origin to three pairs of false natatory feet, composed of a stout and short peduncle, and two oval blades with strongly ciliated borders: the external one very large, and the other very small. Branchice brush-like and fixed on two rows, namely, one above the second foot, and two above the four anterior feet and the external jaw-feet. (M.E.)

Example, Gebia stellata. Length 13 inch. Locality.-Coasts of England. M. Milne Edwards states that this species comes very near to Gebia littoralis.

M. Milne Edwards observes that the Gebice establish the passage between the Thalassinee and the Axia, which last they resemble in the general form of the body and disposi tion of the caudal fin, whilst they approach the first by the conformation of the feet.

Axia Stirhynchus:

a, intermediate antenna; b, external antenna.

Thalassina. (Latreille.)

Generic Character.-Carapace short, narrow, and very much elevated. Stomachal region small and limited backwards by a deep furrow. Cardial and intestinal regions equally separated from the branchial regions, and representing by their junction a triangle, the apex of which is directed backwards. Front armed with a small triangular rostrum. Eyes small and cylindrical. Internal antennæ inserted above those organs; their peduncle of moderate size, and their terminal filaments slender and unequal, the longest about thrice the length of the peduncle. External antennæ very small, their peduncle cylindrical, hardly reaching beyond the rostrum, and presenting above no vestige of appendages. External jaw-feet moderate and pediform, their second joint armed with spiniform teeth on its internal surface, and nearly of the same form as the succeeding ones. First pair of feet narrow and moderately elongated, but rather robust; they are unequal, and the hand which terminates them presents at its anterior and lower angle a more or less strong tooth, which represents an immoveable finger, against which the base of the moveable finger, which is very large, is bent back. Second pair of feet very much compressed, and rather wide; their penultimate joint especially is large and ciliated below. The succeeding feet have nearly the same form, but they are narrower, and less and less compressed. Abdomen very long, narrow, semicylindrical, and nearly of the same size throughout its length. Terminal fin small; the two pairs of lateral blades, formed by members of the sixth ring, nearly linear. False feet fixed to the four middle rings of the abdomen; they are very slender, and composed of a cylindrical and elongated peduncle carrying two more or less ciliated multiarticulate filaments. (M. E.) Example, Thalassina scorpionides. Length about six inches. Colour brownish.

division differ, he remarks, but very little from the first, and the conformation of their thoracic branchiæ does not permit their separation from the macrurous decapods, nor their distant removal from the Thalassinians; but they have respiratory appendages fixed to their abdominal false-feet, exhibiting the greatest analogy with the ramose branchia of the STOMAPODS.

The type of this group, according to M. Milne Edwards. is a small crustacean, to which he gives the generic name Callianidea; but he also arranges in this same division the genus Isea of M. Guerin, under the name of Callianissea, for he thinks that he perceives in this last an analogous mode of organization. If, he observes, the characters assigned to it by M. Guerin be exact, it would be difficult to place this new genus here, and it ought to be approximated to the Pagurians; but it appears very probable to M. Milne Edwards that there has been some error of observation, and that in reality the Isea and Callianide differ but very little. These crustaceans, M. Milne Edwards observes, have all a very small oval thorax compressed laterally: their abdomen, on the contrary, is extremely long and slender. The disposition of the eyes and the antennæ is nearly the same as in Callianassa. The external jaw-feet are pediform, and carry externally a slender and multiarticulate palp. The two first pairs of feet are didactylous; the anterior pair are long, very unequal, and terminated by a stout compressed hand; the second are small and very delicate; the third are enlarged towards the end nearly as in Callianassa, and terminated by a very short tarsus, forming, with a tubercle of the preceding joint, an imperfect claw. The fourth pair of feet are slender and monodactyle; and the fifth pair, small in dimension, are thrown backwards. As in the Crpytobranchids, the abdomen is very long, sufficiently soft, and composed of nearly equal rings, of which the dorsal arch is not prolonged below so as to incase the base of the false feet. The caudal fin offers nothing remarkable; but the false feet, inserted at its lower surface, are furnished with a multitude of branched filaments, which have a structure very analogous to that of branchiæ, and which certainly must be destined to concur in the work of respiration. M. Milne Edwards concludes by observing that this tribe comprehends two genera, one of which appears to him to be too imperfectly known to be conveniently characterized. Callianidea. (Edwards.)

Generic Character.-Body very delicate, slender, and elongated. Carapace hardly a third of the length of the abdomen, and not covering the last thoracic ring, compressed and rather elevated, its lower border applied exactly against the base of the four first pairs of feet. No rostrum, and the anterior border of the carapace notched on each side of the median line for the reception of the base of the eyes, whose peduncles are very short, and formed as in the Callianassa. Four antenna, slender and inserted nearly on the same transversal line; the first pair terminated by two filaments nearly equal in length, one of which however is the largest, and slightly convex towards the end. Appendages of the mouth very small, occupying but little space; mandibles hardly differing from those of Callianassa; valvular appendage of the second pair of jaus very small; external jaw-feet slender and pediform, their second joint furnished internally with a row of dentiform tubercles covered with hairs, and with their three last joints very much elongated. Sternum linear throughout its extent. First pair of feet long, and one of them very stout, with the terminating hand very large, and nearly of the same form as in Callianassa, except that the carpus is smaller. The two succeeding pairs of feet are small and flattened; the fourth pair nearly cylindrical, and their basilary joint very much enlarged. Fifth pair nearly as large as the fourth, and terminating in an imperfect rudimentary claw. Abdomen composed as ordinarily of seven segments, nearly of the same size throughout, and carrying beneath five pairs of false-feet of these the first are reduced to a simple narrow blade slightly ciliated at the end, but the four succeeding pairs have a very remarkable conformation. A peduncle is to be distinguished and three terminal laminæ, two of which are very large and one very small on the edge of the preceding ones; all round the border of the great laminæ a kind of tufted fringe is found, composed of a row of cylinders, each of which gives origin to two smaller filaments, which again in their turn are bifurcated nearly in the same manner as the branchial filaments of the Squille are divided. The five blades of which the caudal

fin is composed are wide and rounded. The thoracic branchia are enclosed as ordinarily in the carapace, and are each composed of cylinders ranged in parallel order on a stem, nearly as in the lobsters, only these organs and filaments are less numerous, and the branchia themselves very small. There are only ten on each side of the body. (M. E.) Example, Callianidea typa. Length about 10 lines. Locality.-Coasts of New Ireland, where it was found by MM. Quoy and Gaimard.

Callianidea typa, magnified.

a, antenna of the first pair; b, external jaw-foot; c, extremity of one of the posterior feet; d, abdominal false feet, first pair; e, false feet of one of the four succeeding pairs; f, marginal fringe of those false feet.

So much doubt exists relative to the genus Isea, Guerin, Callianisea, M. Edwards, that we think we should not be justified in occupying space with the very long and elaborate description of M. Guerin, and the acute criticisms of M. Milne Edwards, who observes that Isea, having been previously employed to designate another crustaceous animal, cannot be retained. M. Guerin's description will be found in the Annales de la Société Entomologique de France,' tom. i., p. 295; and also in M. Milne Edwards's Histoire Naturelle des Crustacés,' tom. ii., p. 322. But though our limits do not permit the insertion of the details, they should be carefully perused by the student, for they are highly interesting and instructive.

FOSSIL THALASSINIANS.

M. Milne Edwards states that the crustaceous fossil found in the chalk formation of Maastricht, and figured by M. Desmarest under the name of Pagurus Faujasii, belongs to the genus Callianassa.

THALASSIO'RNIS, Mr. Eyton's name for one of the ducks (Clangula, Smith), subfamily Erismaturinæ. THA! ASSIOPHYTES (literally sea-plants,' from 9aAaora and púrov) is the name given by Lamouroux to designate the vegetable productions of the ocean and of its rocks and shores. It is equivalent to the term Hydrophytes of Lingbye, and the plants described by Agardh as Marine Algæ. This division of the vegetable kingdom comprehends, in Lamouroux's system, six orders, viz., Fucaceæ, Florideæ, Dictyoteæ, Ulvacea, Aphlomideæ, and Phlomideæ. [SEA-WEEDS; ULVACEE.

THALES (Oans) was a native of Miletus, one of the chief cities of Ionia, and descended from a Phoenician family. Apollodorus, as quoted by Diogenes Laertius, fixes the year of his birth in the first year of the 35th Olympiad, or B.C. 640. Herodotus (i. 74) says that Thales the Milesian predicted the year of the great eclipse which took place while the armies of Cyaxares and Alyattes king of Lydia were engaged in battle. Alyattes became king of Lydia in B.C. 617. Herodotus also says (i. 75) that Thales was in the army of Croesus at the time of the battle of Pterie between Croesus and Cyrus B.C. 547 or 546; at which time he would be ninety-four years old, if the date of his birth is correctly given by Apollodorus. There was a general tradition that he lived to a great age; and Lucian states that Solon, Thales, and Pittacus all lived to be a hundred years old. (On the subject of the eclipse see the article ALVATTES, and Oltmanns, Abhandlungen der Akad. Berlin. 1812-13.)

In the Life of Thales by Diogenes we find numerous traditions attached to his name, the value of which it is somewhat difficult to estimate. Thales is enumerated among the Seven Wise Men, whose wisdom was not the theoretical wisdom of philosophers, but the wisdom of actual life. [BIAS.] Accordingly we find that Thales took an active part in the political affairs of his native country. Before Ionia fell under the Persian yoke, he advised the Ionians to have one common council, and to establish it at Teos, for Teos was in the centre of Ionia; and he further suggested that all the other Ionian states should be reduced to the condition of parts dependent on the government at Teos. Such a scheme, if carried into effect, might have checked the progress of the Persian_arms (Herod., i. 170.) Later writers say that he visited Egypt and Crete in order to improve his knowledge, and that he derived from Egypt his acquaintance with mathematics. There seems no reason for thinking that Thales left any writings. Aristotle at least was not acquainted with any philosophical writings by Thales. Various sayings of Thales are recorded: they are of that sententious character which belongs to the proverb, and they embody truths such as the general experience of mankind recognises; and for this reason they cannot safely be considered as the product of any one mind. Thales is generally considered the founder of the Ionian school; but it is perhaps hardly proper to consider him in any sense as the founder of a school. [IONIAN SCHOOL.] His traditional reputation rested on his physical discoveries and his philosophical speculations. He is said to have been the first astronomer (among the Greeks) who predicted eclipses; and to have discovered the passage (apodos) from tropic to tropic, or, in other words, to have laid down the sun's orbit; and to have fixed the length of the year at 365 days. He determined the magnitude of the sun to be 720 times that of the moon; which is apparently the true version of the corrupt passage in Diogenes. His knowledge of geometry was said to be derived from Egypt, and Pamphila attibutes to him the discovery of the right-angled triangle of the circle (prov KаTaypávaι KUKλov To Tрiywvov opeоywviov), which probably means the demonstration that the angle in a semicircle is a right angle, a discovery attributed also to Pythagoras. Hieronymus says that he measured the height of the pyramids of Egypt by observing the shadow which an object cast when it was of the same length as the height of the object.

The philosophical speculations of Thales, like the earliest efforts of philosophers in all countries, were an attempt to solve the problem that admits of no solution-the real nature of the universe. He is considered by modern writers as the originator of the dynamic philosophy, the nature of which, as opposed to the mechanical, is explained in the article IONIAN SCHOOL. Aristotle (Metaph., i. 3) has explained in a short passage the general doctrine of Thales: There must be,' observes Aristotle, 'some Nature (pious), either one, or more than one, to which all other things owe their origin, this one still subsisting. The number however and the character of such a first principle are not conceived by all in the same way. Thales, the founder of this philosophy, says it is water, and accordingly he taught that even the earth reposes on water, founding this notion probably on the observation that the nourishment of all things is moist, and that heat itself proceeds from water, and that animals live by it: but that from which things come is the origin of all things. He was thus led to this notion, and also by observing that the seeds of all things have a moist nature, and that water is the origin of their nature to all moist things.' Thus the universe contained an active principle by the power of which all things were developed. He considered that the magnet had life, because it attracted iron. The universe then was pervaded by life, or, as Thales expressed it, 'full of gods' (Tavra λion Dewv).

The doctrine of Thales bears some resemblance to systems that have been promulgated in modern times, which have been viewed as atheistical. The assumption of an active power, such as gravitation for instance (though it is not here meant to affirm that gravitation has ever been viewed as a power sufficient for the production and conservation of all things), which is sufficient to maintain all things in a permanent condition (changes such as we observe in limited portions of time and being only continued developments), may be viewed as an hypothesis

made for the purpose of getting rid of the necessity of admitting the existence of God. Those who propound such an hypothesis, without further explanation, certainly do not take much pains to avoid the imputation of atheism. It does not appear however that the doctrine of Thales was anything more than a pure physical theory; and the traditions recorded of him by Diogenes make him a believer in a Diety. The most antient of things existing is God, for he is uncreated; the most beautiful thing is the universe, for it is God's creation.'-It was one of the maxims of Thales, that death did not differ from life. 'Why don't you die then?' said an objector, more witty than wise. Because there is no difference,' was the reply. (Diogenes Laertius, i.Thales;' Ritter, Geschichte der Philosophie, vol. i.)

THALICTRUM (from the Greek Jáλurpov), the name of a genus of plants belonging to the natural order Ranunculaceæ. It consists of herbs which have usually a fetid smell like rue, and hence are called meadow rues. The species have perennial roots with annual stems. The flowers are corymbose, panicled, and somewhat racemose, of a green, white, or yellow colour. They have no involucre and no petals. The calyx is composed of 4 or 5 petal-like sepals. Carpels 4-15 in number. Upwards of 50 species are enumerated, which are mostly natives of the temperate and colder parts of the world.

Th. aquilegifolium, the Feather Columbine, has ovate stipules, placed at the base of the ramifications of the petiole; and a corymbose panicle. It is a native of Europe, in woody districts of Germany, France, and Italy. The stems and stamens of this plant vary in colour, sometimes being greenish-white and sometimes purple. A variety is found in Austria with dark purple stems and stamens, and is called Th. a. atropurpureum. Another variety, formosum, has the stamens dilated at the apex; whilst another has the stems green and stamens quite white, and is named Th. a. album.

Th. minus, Lesser Meadow-Rue, has the stem round, mealy, the flowers panicled, drooping, leaflets smooth, roundish, toothed at apex, glaucous, pericarps acute furrowed. It is a native throughout Europe. In Britain it is found in chalky pastures, and on the sea-coast where shell-sand abounds. The greater meadow-rue, Thalictrum majus, is also a native of Great Britain, though rare.

Th. flavum, Yellow Meadow-Rue, has an erect, branched, furrowed stem, fibrous roots, a somewhat corymbose panicle of cream-coloured flowers, with wedge-shaped, trifid acute leaflets. It is a native of all districts in Europe. In Britain it occupies wet meadows, the banks of rivers and ditches. It has a root of a yellow colour, and is said to resemble, both in appearance and properties, rhubarb. It yields a yellow dye, which may be employed for dyeing wool, and was formerly used as a remedy in jaundice. Like many of the family to which it belongs, it is very acrid, and produces blisters upon the skin, when applied to it.

Th. fœtidum, Fotid Meadow-Rue, has a simple stem, naked at the base, leafy in the middle, and panicled at top; the leaflets are obtuse, toothed, and covered with a clammy pubescence. It is a native of France, Switzerland, Russia, &c., and is found in valleys and on hill sides, and in the fissures of calcarous rocks. It smells more powerfully than any of the species-hence its specific name. Th. Cornuti has dioecious or polygamous flowers, with club-shaped filaments, obovate roundish leaflets, glaucous beneath. This is a North American species, and is found on the banks of rivers and in woody districts throughout the whole continent.

The character of the leaves of these plants and their thickly-flowered panicles render them favourites in gardens. They are readily increased by parting their roots and planting them out in autumn. They flourish best in moist shady situations, but are not particular; they are free-growing plants and well adapted for borders.

THAʼLLEPUS, Mr. Swainson's name for a genus which he places among the Aplysians, apparently upon the authority of one of the late Rev. Lansdown Guilding's drawings.-Ex., Thallepus ornatus. (Malacology.)

THALLI CERA, M. Quoy's name for a genus of Gastropods, placed as the first subfamily (with a ?) of his Turbida (Turbinida, we suppose, is meant), by Mr. Swainson. It is immediately followed by the subfamily Ampullarinæ. (Malacology.)

THALLITE. [EPIDOTE.]

THALLUS is a botanical term used exclusively in cryptogamic botany, and is generally applied to the part of the plant which bears the reproductive organs, and constitutes the principal part of its vegetation. In Jungermanniacea the thallus or frond is either a leafy branched tuft, as in mosses, with the cellular tissue particularly large and the leaves frequently furnished with lobes and appendages at the base, called stipulæ or amphigastria; or it is a flattened mass of vegetable matter seated upon the ground. In lichens the parts which bear the reproductive organs, and which constitute the great bulk of the plant, is called thallus or blastema. In the Algæ the term thallus is applied to the whole plant; whilst in the fungi it is used synonymously with thalamus, to express the mass of fibres from which many of the fungi arise. Thallodes is the adjective used to express anything arising from the thallus.

THAME. [Oxfordshire.]

THAMES, the most important river in Great Britain, rises in the central part of England, and flows eastward into the German Ocean. Our description will comprehend a notice of its basin, course, and affluents, and commercial importance.

Basin. The limits assignable to the basin of the Thames will depend on the place at which the mouth is fixed. The opening between Sheerness in Kent and Shoebury Ness in Essex, between five and six miles wide, is commonly regarded as the mouth of the Thames; but it is preferable in some respects to consider as such the opening between Whitstable in Kent and the east extremity of Foulness Island in Essex, where the tideway has a breadth of eighteen miles. Here the Thames opens into a large bay separating Kent on the south from Essex and Suffolk on the north, and having for its extreme points the North Foreland in Kent and Orford Ness in Suffolk, fifty miles distant from each other. Into this bay several rivers, besides the Thames, open: as the Crouch, the Blackwater, and the Colne, from Essex; the Stour, which separates Essex from Suffolk; and the Orwell, the Deben, and the Alde, from Suffolk.

The basin of the Thames, commencing at Whitstable, is bounded by the high grounds which there run down to the coast, and form the cliffs east of that town. The boundary runs in a very irregular line across the county of Kent and the Weald district of Kent and Sussex to the high ground on the southern border of Ashdown Forest in the latter county. This part of the boundary is very irregular from the manner in which the basin of the Thames is complicated with the basins of the Kentish Stour, the Rother, and the Sussex Ouse.

From Ashdown Forest the boundary runs west-north-west across the high ground of Tilgate and St. Leonard's forests to Leith Hill in Surrey, and thence west-south-west, though in a very irregular line, past the head of the Wey in Woolmer Forest to the verge of the chalk downs near Alton, Hants. This boundary separates the basin of the Thames from the basins of the Sussex Ouse and the Arun. Nearly all the waters which rise along the boundary, from its commencement to Tilgate Forest, flow into the Medway; those from Tilgate Forest to Leith Hill, into the Mole; and those from Leith Hill to Alton, into the Wey.

From the neighbourhood of Alton, the boundary of the basin is formed by the chalk downs which extend across Hants and Wilts by Basingstoke, Kingsclere, Highclere, and Burbage near Great Bedwin; and from thence by the downs which run north-westward to the neighbourhood of East Kennet and Abury. These chalk downs separate the basin of the Thames from the basins of the Anton or Test and the Hampshire Avon: that part of the basin of the Thames which they bound is drained by the Loddon and the Kennet.

From near East Kennet the boundary turns north and north-north-east along the green-sand hills by Compton Basset, Clyffe Pipard, and Chadderton; and from thence westnorth-west to the western extremity of the basin near the commonly reputed head of the Thames amid the Cotswold Hills between Cirencester and Tetbury. The boundary between East Kennet and the Cotswolds separates the basin of the Thames from that of the Bristol Avon, or more correctly of the Severn, of which the Avon is a tributary.

From the neighbourhood of Tetbury the boundary runs northward along the ridge of the Cotswolds, which here separate the basins of the Thames and the Severn, to the