In the aggregates thus exhibited, there is an apparent want of conformity in the relative proportions of each class. This wholly arises from the extinct genera of the ancient strata; for, on making the comparison between the recent series and those of the latest group of deposits, no such difference will be perceived. On the contrary, a considerable agreement between the proportions of existing species and the several classes of fossil shells in the tertiary beds prevails; the average increase of numbers being about sevenfold.

If we follow the investigation further, we may observe that the fossil multilocular and complicated Testàcea, which characterise the oldest formations, and decidedly preponderate in that end of the series, form one fifth part of the entire catalogue; but, amongst the recent shells, this class constitutes less than a fortieth part, and in the tertiary series only a fiftieth part.

The conclusion to be drawn from a summary of facts more numerous, and on a more extended scale than, until recently, has been attainable in this department of natural history, is, that in proportion as we descend the vast series of deposits that overspread this portion of the earth, so do we recede, step by step, from the circle of existing organised beings, and from the phenomena attendant on their structure, their habits, and their adaptations.

February, 1829.

R. C. T.

ART. VIII. An Account of a new Species of Trilobite, found in the Barr Limestone in the Neighbourhood of Birmingham. By Frederick JukES, Esq. With a Note by J. D. C. SOWERBY, Esq.

Sir,

ALLOW me to present to you the enclosed drawings of a curious fossil (figs. 8, 9, 10.), discovered in the lime quarries at Hay Head, near Great Barr, a village about nine miles from this town. It appears to be of the Trilobite kind, retaining a considerable quantity of a fine crustaceous covering of a dark brown colour, and highly polished. The drawings represent its exact size, measuring in length about 5 in., and in width 34 in., being much larger than fossils of that character usually found in this country. The Trilobites already discovered in the Dudley lime formation are of two kinds; viz. one which is commonly called the Dudley fossil (fig. 11.), and mentioned in Parkinson's work upon Organic Remains, and another (fig.

12.), which, I believe, has not yet been particularly noticed, arising, probably, either from their scarcity, or from the imperfect condi

tion in which

they are usually

found, the head

and tail being generally apart. The points of difference in the

Dudley Trilobites may be seen by the accompanying sketches, which

are taken from

8

2

specimens in my possession. (See figs. 11, 12.) Mr. Payton of Dudley has been at the pains of having similar fossils drawn upon stone, in a masterly manner, by Mr. G. Scharf, which

also represent their differences most satisfactorily. These have a crustaceous covering, and twenty-four transverse lines or ribs across their lobes.

The Trilobite from Barr, which I have in my possession, has a very remarkable appearance, and differs in so many respects from the Dudley Trilobites, that it can scarcely be classed with those fossils. It has ten transverse lines across

the lobes, covering only the upper half of the body, the lower half being a smooth surface to its termination. The lobes (if

they may be so called) do not extend lower than the transverse lines, and their division is so unequal that the middle lobe is almost four times the width of those of the side. This animal has probably had the power, like the Dudley Trilobites, of coiling itself up, by making the tail meet the mouth; and, from the curvature at the lateral termination of the transverse

lines, which give the appearance of side lobes, this is not an improbable supposition. The head, which, perhaps, is the

most peculiar

part, occupies nearly a third of the animal.

The eyes are very prominently marked, exhibiting the palpebræ, or eyelids, dis

tinctly and par

12

tially open, surrounded by an orbital margin, with a sort of notch in the superior part. From each canthus, or corner of the eye, there is a kind of suture extending to the under

surface of the head. There is also a small tuberosity situated in the centre of the head between the orbits.

Lime formations in this country, if we may judge from the fossils they contain, appear to be of great variety and strangely dispersed throughout the western side of the island. The Dudley lime is considered by geologists to be transition limestone, and from its immediate vicinity to the trap rocks of Rowley, it is reasonable to suppose that it has been raised from a great depth below the surface, by some volcanic action. The Castle Hill at Dudley, consisting of limestone, is not a quarter of a mile from Cawney Hill, which is composed of basaltic columns. The lime strata of Dudley dip principally to the east and to the west, and are raised in the shape of a cone, with their lines of continuity at the summit broken away. (fig. 11.) The dip to the east appears to pass under

,

the Wednesbury coal field, and to crop out again at Walsall, a distance of nine miles, where it is recognised by the fossils bearing an exact resemblance. It is singular that at this place it should be again accompanied by the trap rock, which appears at Pouch Hill *. situated at a distance of little more than a mile. Hay Head, in the parish of Barr, is situated about two miles east from Walsall, and is the spot where this singular Trilobite was discovered. The limestone here appears of a darker colour, more condensed, and is slacked with less facility than that of Dudley or Walsall, and appears from its outcrop to be an under-stratum. The Orthoceratite, I believe, has never been discovered at Dudley, but in these quarries most beautiful specimens of that fossil are frequently found, and of considerable magnitude.

I remain, your obedient servant,

FREDERICK JUKES.

General Hospital, Birmingham, Nov. 12. 1828.

THE Dudley fossils have so long been objects of admiration. among naturalists, that it is a remarkable fact that so large and

* At this place fine specimens of Radiated Zeolite and Prehnite are found.

handsome a species as the one found in the Barr limestone (figs. 8, 9, 10.) should have remained undiscovered in England until now. It certainly was not known when M. Alexandre Brongniart published his account of that tribe of fossils. The Dudley fossil had long obtained the name of Trilobite (from the three-lobed form of the body); but, as considerable difference was observed among the several species found at Dudley an other places, M. Brongniart judged it necessary to divide them into five genera or subgenera, Calymène, A'saphus, Ogygia, Paradoxides, and Agnóstus. The common Dudley fossil is the Calymène Blumenbáchii (fig. 11.), the scarce one is A'saphus caudàtus (fig. 12.); and these are all that were known at or near Dudley. Your correspondent, J. A. H., has supplied you with a figure of A'saphus Debùchii (fig. 27.), found in Radnorshire, which is a much larger species than either of the Dudley ones, but not equal to that from Barr. The Honourable William Strangeways found at Calomenca, in Russia, a Trilobite, agreeing apparently with this large one, and M. Adolphe Brongniart obtained, during his travels in Sweden, in 1825, specimens of the same species at Husbifjol, near Linkoping. It was immediately seen that this did not belong to either of the divisions above referred to, he therefore proposed to treat of it as the type of a new genus to be named in an appendix to the Histoire Naturelle des Crustacés Fossiles, which, if published, has not yet reached England. (Drawings and specimens are in the possession of Charles Stokes, Esq. M.G.S., to whom I am indebted for this information.) In the Annals of the Lyceum of New York, for December, 1824, (vol. i. No. 6.) observations, with figures, are given by Mr. Dekay, upon a new genus of Trilobite discovered at the Trenton Falls, upon West Canada Creek. He has named it Isótelus, from isos, equal, and telos, end; the two extremities being nearly alike. It differs from the Barr Trilobite chiefly in the number of the divisions of the body, having only eight instead of ten; a difference scarcely sufficient among Trilobites, for a generic character, but excellent for the distinction of sections or species.

As Trilobites occur only in transition rocks, and the lowest beds of the mountain limestone, their presence in any country is an important geological feature; and since it further appears that the different species are peculiar to different beds, a means is pointed out of identifying these beds or strata, as in the case of the Barr limestone, at immense distances.-J. D. C. S.