402 Proceedings of the Ohio State Academy of Science. 



The shell is characterized by its small size and rapidly 



enlarging whorls. 



Horizon and locality. — Maxville limestone. 



Upper zone: Below Thompson Residence, White Cottage. 



Undetermined zone: jMiddle of Cut No. 6, Mt. Perry-Fulton- 

 ham. 



NATICOPSIS ZIGZAG— Whitfield. 



1882. Naticopsis ziczac. Whitfield, Ann. N. Y. Acad. Sci., Vol. II, p. 223. 



Maxville limestone : Newtonville, Ohio. 

 1891. Naticopsis ziczac. Whitfield, Ann. N. Y. Acad. Sci., Vol. V, p. 

 590, pi. 14, figs. 15, 16. 

 Maxville limestone : Newtonville, Ohio. 

 1895. Naticopsis ziczac. Whitfield, Geol. Surv. Ohio, Vol. VII, p. 477, 

 pi. 10, figs. 15, 16. 

 Maxville limestone : Maxville, Ohio. 

 1909. Naticopsis ziczac. Grabau and Shimer, N. A. Index Foss., p. 673, 

 fig. 933. 

 Maxville : Ohio. 



Description. — Shell less than medium size with depressed 

 spire. Whorls ventricose, about two and a half in number, 

 rapidly increase in size. Aperture large, equal to about half the 

 size of the whole shell, rounded. Suture prominent, subquadrate 



Fig. 27. — Naticopsis ziczac. 



a and b. — -Natural size and enlarged views of an individual. (After 

 Whitfield.) 



in cross section. Surface of the whorls of the spire crossed 

 by transverse striae, which are bent backward. Surface of the 

 body whorl also ornamented with transverse striae which bend 

 backward in the sutural third of the whorl, then by acute bends 



