70 PALEONTOLOGY OF NEW YORK. 



MERISTA, SuEss. 1851. 



PIRATE XLVI. 



1851. Merista, Suess. Branhiopoden der Koessener Schichten, p. 17, pi. i. 



1851. Merista, Suess. Jahrb. der k. k. g-eolog-. Reichsanst, vol, iv, p. 150. 



1856. Merista, Suess. Classification der Brachiopoden von Th. Davidson, \>. 85, pi. iii, figs. 18-20. 



1859. Camarium, Hall. PaliEontology of N. Y., vol. iii, pp. 486-488, pi. xcv, fig-.". 2-6. 



1859. Camarium, Hall. Twelfth Rept. N Y. State Call. Nat. Hist., p. 42. 



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

 1862. Camarium, Hall. Fifieenth Rept. N. Y. State Cab. Nat. Hist., pp. 176, 181, figs. 10-13. 

 1867. Merista, Hall. Twentieth Rept. N. Y. State Cab. N.-it. Hist., p. 258. 



1881. Merista, D.avidson. Geological Magazine, new series, vol. viii, p. 289. 



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



Diagnosis. Shells transverse or elongate, l)oth 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 

 rare 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 figures of Merista hertiilea, Barrande, the type-species, given by Mr. DAvrosoN (Supplement 

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

 ever, in Babbande's figures, lioth of this species and of M. passer, Barrande (Systeme Silurien, vol. v, 

 pis. X, xiii, xiv), and in A.merican species of this genus. 



