70 PALEONTOLOGY OF NEW YORK. 



MERISTA, SuEss. 1851. 



PLATE XLVl. 



1861. MeriHa, Sobss. Brar.hiopoden der Koessener Schichten, p. 17, pi. i. 



1851. Meriata, Subsb. Jahrb. <lei- k. k. freolog. Roichsanst, vol, iv, p. 150. 



1866. Meritta, Sdbss. ClHssificalion der Brachiopoden von Th. Davidson, p. 85, pi. iii, ligs. 18-20. 

 1869. Camariwii, Hall. Palffiontology of N. Y., vol. iii, pp. 486-488. pi. xcv, <i(fs. 2-6. 



1859. Camanwn, Hall. Twelfth Kept. N Y. State Cab. Nat. Hist., p. 42. 



1860. Meritta, Hall. Thirteenth Kept. N. Y. State Cab. Nat. Hist., pp. 73, 93, figs. 10-13. 

 1863. Oamarium, Hall. Fifieenth Kept. N. Y. State Cab. Nat. Hist., pp. 176, 181, figrs. 10-13. 



1867. Merista, Hall. Twentieth Rapt. N. Y. State Cab. Nat. Hist., p. 258. 



1881. 3feri«to, Davidsox. Geological Magazine, new series, vol. viii, p. 289. 



1882. Merista, Davidson. British Silurian Bi-achiopoda, Supplement, p. 103, pi. v, figs. 10-13. 



DiAQNOSis. Shells transverse or elongate, both valves generally inflated ; 

 anterior margin sinuate, producing a fold and sinus on the marginal portion of 

 the brachial and pedicle-valves respectively. 



In the pedicle-valve the apex is perforated by a circular foramen, which, 

 however, is usually concealed at maturity, by the incurvature of the beak ; 

 deltidial plates rarely retained. On the interior the teeth are prominent and 

 are supported by dental plates which extend either for a short distance into 

 the interior cavity or are considerably produced at their bases as thickened 

 ridges. Between the dental plates is an arched free plate (the " shoe-lifter " 

 process) attached by its posterior and lateral margins, but at its anterior mar- 

 gin extending beyond the dental lamellae and rising in a low, broad curve. In 

 riire instances this process, from its origin, bears a sharp median carina which 

 makes the anterior margin highly angulate. The muscular area appears to be 

 limited to the space between the dental lamellae and to the surface of the 

 " shoe-lifter." 



In the brachial valve a median septum is more or less strongly developed,* and 

 divides a simple ovate adductor impression. The hinge-plate is short and deeply 

 divided by a median groove. The brachial supports consist of spiral cones 

 with their bases in apposition and parallel to the axial plane of the shell, and 



* In the 6gfare8 of Merista herculea, Barrande, the type-species, given by Mr. Davidboh (Supplement 

 British Silurian Brachiopoda, pi. v, figs. 10, 13), no evidence is seen of this dorsal septum ; it appears, how- 

 ever, in Babrahdii's figures, V>oth of this siiecies and of M. passer, Barrande (Systfime Silurien, vol. v, 

 pis. s, ziii, dr), and in A.merican species of this genus. 



