392 Proceedings of the Ohio State Academy of Science. 



gin, often forming undulations of the surface [Whitfield, 1895]." 



Length 70 mm. 



This species is readily distinguished by its triangular out- 

 line and radiating plications. 



Horizon and locality. — JMaxville limestone. 

 Upper zone : Thompson Residence, White Cottage. 

 Shale-nodular zone : Kroft Bridge, White Cottage. 



ALLORISMA ANDREWSI-Whitfield. 



1882. Allorisma Andrezvsi Whitfield, Ann. N. Y. Acad. Sci., Vol. 11^ 

 p. 222. 

 Maxville limestone: Newtonville, Ohio. 

 1888. Allorisma Andrezasi. Herrick, Bull. Denison Univ., Vol, IV,. 

 pi. 11, fig. 12. 

 Chester limestone : Ohio. 

 1891. Allorisma Andrezvsi. AVhitfield, Ann. N. Y. Acad. Sci., Vol. V,. 

 p. 588, pi. 14, figV 6. 

 Maxville limestone : Newtonville, Ohio. 

 I«y5. AUorisvia Andrezvsi. Whitfield, Geol. Sun.'. Ohio, Vol. VII, pv 

 473, pi. 10, fig. 6. 

 Maxville limestone: Newtonville, Ohio. 



Description. — Shell of medium size or larger, transverse 

 outline obovate, longitudinal outline subrectangular. Valves 

 ventricose, most so along a line extending diagonally from the 



Fig. 18. — Allorisma andrezvsi. A view of the right valve. (After Whit- 

 field.) 



beak to the posterio-ventral angle, and with a slightly concave 

 line parallel with and dorsal to the former. Ventral margin 

 convexly curved and parallel with the dorsal margin. Posterior 

 margin broadly rounded. Anterio.r margin more abruptlj 



