586 Contributions to Invertebrate Palaeontologtj. 



bratula) ambigua, of the European Carboniferous rock. The Ohio 

 specimens are equally characteristic in form with any of those from 

 the West, and may be readily distinguished by its strongly trilobate 

 form. 



Locality. — Newtonville and Maxville, Ohio. 



Genus TEREBRATULA Llliwyd. 



Terebrattila turgida. 



Plate XIII, figs. 21 and 22. 



Terebrattila tunjidu Hall, Trans. Albany Inst. vol. iv, p. 6, extract page 6, 1S5G. 



Shell rather smaller than medinm size, ovate in general form, the point of 

 greatest width usually below the middle of the length, and the length nearly 

 one-third greater than the transverse diameter ; base truncate and slightly 

 eniarginate. Valves moderately to highly ventricose, the ventral generally 

 the deepest and sinuate below the middle of the length, often deeply so ; beak 

 strong, incurved, obliquely and very distinctly truncate, and perforated by a 

 I)roportionally large foramen. Dorsal valve highly convex, with an abruptly 

 incurved beak, which passes within the deltidial opening of the opposite valve ; 

 front of the valve sometimes convex and sometimes slightly sulcated, causing 

 the emargination or truncation of the base. Shell structure finely punctate, 

 and the surface often ornamented by concentric varices of growth. 



The specimens from Ohio are larger than those from -the typical 

 locality (Spergen Hill, Ind.), usually are, but not so large as they 

 are sometimes found. They correspond closely in form and general 

 characters, but are not so generall}' sulcated on the dorsal valve. 

 They are, however, altogether too similar to afford moans for specific 

 distinction. The most of the specimens which I have examined 

 from Ohio have been slightly distorted by compression, and in this 

 condition may not afford as many points of difference as more per- 

 fect individuals would have done. 



Formation and Locality. — In the Maxville limestone at Maxville 

 and Newtonville, Ohio. 



MOLLUSCA. 



LAMELLIBRANCIIIATA. 



Pinna Itfaxvillensis. 



Platk XIV, fig. 5. 



Pinna Maxvillensis Whitf., Ann. N. Y. Acad. Sci., 1SS2, p. 221. 



Shellof about a medium size, very acutely triangular in outline, with highly 

 convex valves ; the length along the hinge equal to nearly three times the 



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