CONTRIBUTIONS TO PALEONTOLOGY. 29 



Surface marked by tine concentric strise and faint radiating un- 

 detiiied lines. 



This little species scarcely ever exceeds two-tenths of an inch in length ; 

 while the greatest breadth, which is anterior to the middle, is nearly the 

 same. The dorsal valve has the appearance of a Lingula, with flattened 

 margin extending beyond the beak : the ventral valve shows a submarginal 

 foramen. The muscular impressions (which are faintly preserved) differ from 

 the ordinary DisciNA, but are too obscure to afford means of separating it 

 from the genus. 



In some specimens the posterior margin is abrutly rounded, while in 

 others it is straightly truncate. It may, perhaps, have been an elongated 

 form of this shell which is figured as Lingula concentrica in the Geological 

 Ileport on the Fourth District. 



Geological formation and locality. In the Grenesee slate : near Lodi, and 

 at Bigstream point, Seneca county. 



" DISCINA NEGLECTA ( n. s.)." 



Shell elliptical. Dorsal valve convex : elevation of the apex 

 above the plane of the margins about one-twelfth of an inch ; 

 apex situated about one-third the length of the shell from the 

 posterior margin. 



Surface marked by crowded wrinkled concentric strise. 



A single specimen of the impression of the dorsal valve measures seven- 

 tenths of an inch in length, with a width of six-tenths of an inch. The dorsal 

 valve of another specimen of similar character is more nearly circular, the 

 concentric strise are thin and elevated, and the interior shows a linear 

 muscular impression. 



Other specimens are required for a full determination of the characters 

 of the species. It is a more robust form, with the apex more elevated, than 

 the D, lodensis ; and the specimens may be compared with D. seneca. 



Geological formation and locality. In the arenaceous shales of the Che- 

 mung group, from the Inclined plane at Ithaca, Tompkins county. 



" DISCINA ELMIRA ( n. s.)." 



Dorsal valve very convex, transversely broad-oval ; breadth about 

 seven-tenths of an inch, and length half an inch : apex ex- 

 ce^itric, or about one-third from the posterior margin. Ventral 

 valve unknown. 



Surface marked by extremely fine crowded strise. 



This specimen of the dorsal valve only, is noticed in anticipation of 

 obtaining materials for a full illustration. In the elevated dorsal valve, 

 position of apex, and fine striae, it bears some resemblance to the dorsal 

 valve of D. grandis. 



