376 Proceedings of the OJiio State Academy of Science. 



Whitfield, Geol. Surv. Ohio, Vol. 



Grabau and Shimer, N. A. Index 



1895. Spirifera (Martiiiia) contracta. 

 VII, p. 471, pi. 9, figs. 17-19. 

 Maxville limestone : Ohio. 

 1909. Martinia glabra var. contracta. 

 Foss., p. 341. 

 Chester : Illinois, Ohio and Nevada. 



Description. — ■ Shell of medium and of larger than medium 

 size, fairly robust, broadly ovate in general outline. 



Ventral valve robust, with incurved beak. Hinge line short, 

 -equal to half the width of the shell. Area small, divided by a 

 rather large triangular pedicle opening. ]\Iedian sinus shallow, 

 narrow, and indistinct on the beak, but gradually increasing in 

 width toward the anterior end where it is somewhat extended 

 into the fold of the opposite valve. 



Pig. 10. — Martinia contracta. 



a. — Dorsal view of the t.vpe specimen from the Chester limestone 



of Illinois, 

 b and c. — Dorsal and profile views of a Maxville specimen. -(After 



Whitfield.) 



Brachial valve less convex and nearly circular in outline, 

 with minute beak. Median fold developed only in the anterior 

 lialf toward which margin it increases in size. 



Surface marked by very minute radiating plications, which 

 alternate in size and which are crossed by still finer concentric 

 lines. 



Length 14-35 nim. ; width 14-40 mm. 



The shell is characterized by its robust form and by the 

 Tninute radiating plications and the finer concentric lines. Frag- 



