APPENDIX E. — PALEONTOLOGY. 177 



sinus, and the ventral valve a correspondingly elevated ridge. Others 

 are depressed, with scarcely any sinus or bourrelet. The specimens I 

 have seen from Arkansas are considerably mutilated. Occurs in Wash- 

 ington county. 



Terebratuxa marcyi, Shumard. 

 Paleontology, PL 1, fig. 4, a, b. 



Shell small, ovate, elongate, moderately convex, sides and front neatly 

 rounded ; dorsal valve regularly convex, rather more gibbous than the 

 opposite valve, greatest height near the beak, no traces of sinus ; beak 

 elongated, elevated incurved, no perforation visible in our specimens ; 

 ventral valve without median ridge, pointed at summit, cardinal border 

 slightly sinuous. Surface of each valve marked with from thirty-four 

 to thirty-eight simple rounded striae, which commence at the beak and 

 proceed to the lateral borders and front with division. In general form 

 it resembles T. serpentina of Koninck, (Descr. des Animaux fossiles, 29, 

 pi. xix, fig. 8, a — e,) but its smaller size and the lesser number of striae 

 will serve to distinguish it. 



It occurs with Terebratula subtilita and Productus punctatus in 

 Washington and Crawford counties, Arkansas, in dark-grayish carbon- 

 iferous limestone. We have found the same species in Floyd county, 

 Indiana. 



Spirifer, (indet.) 



Paleontology, PL 1, fig. 3. 



In the collection from Washington county are several casts of a 

 spirifer like that which we have figured. They are all too imperfect foE 

 description. 



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