114 



PALEONTOLOGY OF NEW YORK. . 



being lost. The teeth are supported by dental plates and between them lies a 

 broad median ridge which narrows as it approaches the hinge. The brachial 

 valve has a broad, full beak, which is closely incurved and concealed beneath 

 the deltidium of the opposite valve. The cardinal process is large, erect and 

 slightly bilobed on its posterior margin ; it rests upon a short plate bearing two 

 ridtres which are continued into the bases of the crura. On either side of these 

 ridges and just within the margins of the valve, is a strong, oval, concave, 

 pouch-like plate. The crura are very long, passing into the primary lamella3 

 without interruption. The spirals are relatively small, situated anteriorly, and 

 consist of seven or eight volutions. These are connected by a simple erect loop, 

 which is situated medially, and terminates at the junction of the lateral branches 

 in a short, horizontal process. 



External surface of the valves covered with numerous radiating plications ; 

 occasionally smooth. Shell-substance fibrous, impunctate. 



Type, Terebratulites gryphm, Schlotheim. Stringocephalus limestone (Middle 

 Devonian). 



Observations. Our knowledge of this old genus is still imperfect in many 

 important respects, especially in regard to the 

 muscular and other markings on the internal sur- 

 faces of the shells. Mr. Davidson has elucidated 

 the character of the spirals, loop, hinge-plate and 

 cardinal process,* and his restoration of the 

 brachial apparatus and its attachments is here in- 

 troduced. 



Qdensted, in 1871, describedf a shell from the 

 Carboniferous limestone of Ratingen, as Uncites car- 

 bonarius, a striated species, having the biconvex ex- 

 terior of Uncites ; the form is, however, little known 

 audits internal structure has not been demonstrated. 



* Geological Mag-azine, New Series, vol. viii, p. 145, 1881 ; and Devonian Biat-hiopoda, Supplen}erit, 

 p. 30, 111. iii, figs. 5-10, 1882. 



t Op. cit., p. 520, pi. liv, tigs. 47, 48. 



Fig. 103. 

 Iiiteiior of brachial valve of Uncites gry- 

 phus, Schlotheim ; showing cardinal 

 process, marginal pourlies, spii'al and 

 loop. (Davidson.) 



