S88 PALAEONTOLOGY OF NEW-YORR. 



Surface marked by fine close concentric striae which are neatly rounded 



on well-preserved specimens, and at intervals are crowded into more 



prominent ridges. Shell-structure punctate. 



On cutting down a specimen of this species, it has been found to pos- 

 sess a short simple loop, without appendage, as in Terebratula. 



The larger specimens are about three-fourths of an inch in length. 



Tho shell is readily dictingiiished by its elongate form, moderate convexity, 

 truncate or sinuate front, and median depression in the ventral valve ; features 

 whieh I have not observed in any other species in this geological formation. 



Geological formation and localities. This species occurs in the Upper Ilelder- 

 berg limestone, at Columbus and Sandusky, Ohio ; and in the neighborhood of 

 Cayuga, Canada West. 



Terebratula lianiionia (n. s.). 



PLATE LX. 



Shell ovate or subspatulate, tapering somewhat abruptly to the beak, 

 convex in the middle and compressed at the margins. 



Ventral valve regularly arcuate from beak to front, moderately convex 

 in the middle, a little gibbous above and depressed-convex or slightly 

 concave towards the front, the upper part narrowing ; the beak much 

 extended, attenuate and arcuate, but not closely incurved ; apex per- 

 forate, the slope to the cardinal margin scarcely concave : deltidial 

 plates large. 



DoBSAL valve moderately convex, some^mes a little more prominent 

 along th^ middle in the upper part, and depressed towards the front 

 and sides. 



Surface marked by fine concentric lines of growth ; the substance of 

 the shell finely punctate. 

 A well-marked specimen of this species has been cut down on the 



dorsal side, revealing the loop, the divisions of which extend for more 



than one-third the length of the dorsal valve ; the angle of return being 



visible, but not the connecting portion. 



