60 Brachiopoda of the Cincinnati Group. 



Ventral valve with its greatest convexity behind the middle ; mesial 

 sinus almost obsolete, or only consisting of a slight flattening along the 

 middle of the anterior slope, on each side of which the lateral slopes 

 are sometimes very slightly compressed ; beak only moderately 

 prominent, obtusely pointed, and strongly incurved upon that of the 

 other valve, while on each side of it a slight carination extends 

 laterally, so as to give somewhat the appearance of a false area. 

 Surfxce ornamented by fine, even, simj)le, radiating striae. Interior 

 unknown. 



Length of medium sized specimen, 0.61 inch; breadth, 0.52 inch ; 

 convexity, 0.34 inch. 



Found in the upper part of the Cincinnati Group, at an elevation of 

 about 600 feet above low water-mark, near Clarksville, in Clinton 

 county, Ohio, and about ten miles south of Maysville, Kentucky. It 

 i s regarded as a rare fossil. 



Genus Treviatospira — (Hall, 1859). 



[Etym. — trenia, foramen; speira, spire.] 



Shell transverse, elliptical or subrhomboidal, inequivalve, furnished 

 with internal spires (arrranged as in sjnrifer). Hinge line shorter 

 than the width of the shell ; cardinal angles rounded. Valves articu- 

 lated by teeth and sockets; beak of ventral valve produced or 

 incurved, and truncated by a small, round perforation, separated from 

 the hinge line by a deltidium. A deep, triangular pit, or foramen, 

 beneath the beak of the ventral valve, which is filled by the closely 

 incurved beak of the dorsal valve. False area sometimes defined. 



Surface marked either with strong, simple plications, or finer fascicu- 

 late or bifurcating strise, which cover also the mesial elevation and 

 depression. Shell structure punctate. 



This genus is regarded by some authors as a synonym for Retzia. 

 (King, 1850). 



Trematospira (f) quadripKcata — (S. A. Miller). 



[E(y7n. — Quadriplicata, in allusinn to the four costce on the mesial elevation of the dorsal valve.] 



Shell transversely suboval, subglobose ; dorsal valve most convex; 

 posterior lateral margins somewhat straightened and converging to the 

 beak ; lateral margins rounded to the front, which is nearly straight in 

 the middle; area none. 



Dorsal valve strongly convex, most prominent in the middle 



