390 Procccdiiujs of the Ohio State Acadciiix of Science. 



PHYLUM MOLLUSCA. 

 CLASS PELECYPODA^ 



SCHIiODUS CHESTERENSIS-Meek , nd Worthen. 



1860. Scliicodiis Clicsfcrciisis. Meek and W'orthen, Proc. Acad. Nat. 

 Sci., Phil., p. 457. 

 Upper Chester limestone: Chester, Illinois. 

 1866. Scliisodus chesterensis. Meek and Worthen, Geol. Svirv. 111., Vol. 

 II, p. 301, pi. 23, figs. 6a, b. 

 Chester group: Chester, Illinois. 

 1891. Sclxizodits Clicstcrcnsis. Whitfield, Ann. N. Y. Acad. Sci., Vol. 

 V, p. 587, pi. 14, fig. 4. 

 Maxville limestone: Maxville, Ohio. 

 1895. Sc!n::odiis Clicstcrensis. Whitfield, Geol. Surv. Ohio, Vol. VII, 

 p. 474, pi. 10, fig. 4. 

 Maxville limestone: Maxville, Ohio. 



Description. — "Shell of mediimi size. tran.sversely .sub- 

 ovate, with moderately convex valves and large, strong, in- 

 curved, and projecting beaks. Anterior end forming one-third 

 the length of the shell, inflated, and rapidly sloping from the 

 beaks to the longest point, which is near the middle of the 

 height, and roimding backward below ; posterior end elongated 



Fig. 16. — Scliicodus clicstcrcnsis. A view of the left valve. (After 

 Whitfield. ) 



and narrowed, obtusely pointed at the extremity ; basal margin 

 irregularly convex, most strongly arcuate opposite the beaks ; 

 posterio-cardinal margin sloping somewhat rapidly from the 

 beaks backward, and the cardinal slope rather abrupt. Surface 

 of the shell smooth, except for the fine lines of growth [Whit- 

 field. 1895]." 



