364 PALEONTOLOGY OF NEW YORK. 



Semincla Rooersi, sp. nov. 



PLATE XLVU, FIGS. 1-i. 



Shell rather small, suboval in outline. Valves subequally convex. Pedicle- 

 valve with a low, broad median sinus and brachial valve with a corresponding 

 fold, both becoming more distinct toward the anterior margin. Lateral slopes 

 depressed-convex. Umbones not conspicuous ; deltidium concealed. 



External surface smooth. 



A normal individual measures 15 mm. in length, and 13 mm. in greatest 

 width. 



Pendleton sandstone (Schoharie grit). Pendleton, Indiana. 



Athtris densa, sp. nov. 



PLATE Xr-VI, FIGS. 6-li. 



Shell transversely elongate, valves compressed ; median fold and sinus not 

 conspicuously developed. Pedicle-valve shallow, with broad, sharply angled 

 cardinal slopes, greatly thickened interiorly. The anterior margin is frequently 

 extended into a linguate process at the termination of the median sinus. 

 Brachial valve the more convex, with an indistinct, flattened, and sometimes 

 broadly grooved median fold with regular and even lateral slopes. In the 

 interior of the valves the form of the muscular scars is normal, though there is 

 a notable variation in the size of the diductor scars. 



St. Louis group. Washington county, Indiana ; Colesburgh, Kentucky. 



Seminula Dawsoni, sp. nov. 



PLATE XL VII, FIGS. 32-Sl. 

 (See pages 95, 96.) 



This species was originally identified as Aihyris subtilita. Hall, by Davidson 

 (Quarterly Journal of the Geological Society of London, vol. xix, 1863). Its 

 diflferences from this species are indicated on the pages referred to. 



Carboniferous limestone. Windsor, Nova Scotia. 



