98 [Assembly 



CLIODERMA ANATIFORMIS. 



Tellinomya anatiformis : Pal. New York, Vol. I, pa. 154, pi. 34, f. 7. 



This specimen is essentially a cast, with little of the shell remaining, 

 and has the appearance of a bivalve shell. The inequilateral char- 

 acter is due to distortion from pressure, and partly to the imperfect 

 separation of the specimen from the adhering roct. The divergent 

 grooves are apparently caused by the thickening at the junction of the 

 ventral partition with the outer shell. The species is extremely broad, 

 and the postero-lateral margins are much expanded. A small portion 

 of the shell towards the apex shows a sharp dorsal carina. 



Geological formation and locality. In Trenton limestone : Watertown, 

 N.Y. 



CLIODERMA EXPANSA. 



Delthyris expansus : Emmons, Geol. Report Second District, p. 397, f. 2. 



This fossil belongs to the Genus Clioderma, having a great lateral 

 expansion and a very strong dorsal carina. 



I have before me an imperfect specimen apparently of this species, 

 which has a length of more than an inch and three-fourths on thie carina. 



Geological formation and locality. Same as the preceding. 



CLIODERMA ATTENUATA. 

 Clioderma attenuata : Geol. Keport of Wisconsin. , 



This species, of the Trenton limestone in Wisconsin, is ovate-triangu- 

 lar in form, the dorsum abruptly and prominently carinate, the cavity 

 very shallow, and the apex attenuate. 



The casts of this species show a feature which is apparently of generic 

 importance. The apex of the cast is trifid, from two parallel short ver- 

 tical septa which divide this portion of the shell into three divisions for 

 a short distance below the summit. 



This species resembles the C. canaliculata in form, but has no depres- 

 sions of the shell parallel to the sides, and the surface is apparently less 

 distinctly striated. 



Geological formation and locality. In Trenton limestone of Wisconsin. 



