New Species of Trilobite. 45 



handsome a species as the one found in the Barr limestone {Jigs, 

 8, 9, 10.) should have remained undiscovered in England until 

 now. It certainly was not known when M. Alexandre Bron- 

 gniart published his account of that tribe of fossils. The Dud- 

 ley 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, Calymene, A^saphus, 

 Ogygirt:, Paradoxides, and Agnostus. The common Dudley 

 fossil is the Calymene BlumenbachzV [Jig. 11.), the scarce one 

 is A^saphus caudatus {Jig» 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^saphusDebuch«'(^y^. 2 7. )j found 

 in Radnorshire, which is a much larger species than either of 

 the Dudley ones, but not equal to that from Barr. The Ho- 

 nourable 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 pro- 

 posed to treat of it as the type of a new genus to be named in 

 an appendix to the Histoire Natiirelle des Crustaces 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 Tren- 

 ton Falls, upon West Canada Creek. He has named it Iso- 

 telus, 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 often ; 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. 



