384 Proceedings of the OJiio State Academy of Science. 



1895. Seniinula subquadrata. Hall and Clarke, Pal. N. Y., Vol. VIII, 

 pt. II, pi. 47, figs. 7-9, 15, 16; pi. 84, figs. 30, 31. 

 Kaskaskia limestone : Chester, Illinois ; Crittenden County, Ken- 

 tucky. 

 St. Louis limestone : Pella, Iowa ; Spergen Hill, Indiana. 

 1895. Athyrls subquadrata. Whitfield, Geol. Surv. Ohio, Vol. VII, p. 

 472, pi. 10, figs. 1-3. 

 Maxville limestone : Newtonville and Maxville, Ohio. 

 1897. Athyris subquadrata. Weller, Trans. N. Y. Acad. Sci., Vol. XVI, 

 p. 258, pi. 19, fig. 16. 

 Batesville sandstone : Batesville, Arkansas. 

 1903. Seniinula subquadrata. Girty, U. S. Geol. Surv., Prof. Paper 16, 

 p. 296, pi. 1, fig. 5. 

 Leadville limestone : Leadville district, Colorado. 

 Millsap limestone : Castle Rock quadrangle, Colorado. 

 1909. Seiniinila subquadrata. Grabau and Shimer, N. A. Index Foss., 

 Vol. I, p. 354. 

 Kaskaskia: Ohio, Kentucky, Illinois, Utah. 



Description. — Shell of medium size or smaller, subquadrate 

 in outline, wider than long in most specimens ; the widest portion 

 being anterior of the middle. The bunching of the concentric 



a D c 



Fig. 13. — Seniinula subquadrata. 



a and b. — Dorsal and anterior views of the same specimen, 

 c. — Dorsal view of another individual. (After Whitfield.) 



lines of growth at the anterior end often gives a thickened ap- 

 pearance to the shell. 



Pedicle valve ventricose at the posterior end, with extended 

 and incurved beak, the extremity of which is truncated thus 

 forming a round foramen. Mesial sinus increasing in depth and 

 breadth toward the anterior end, and culminating in a lingual 

 extension, limited on either side by a lateral fold. 



