144 CARBONIFEROUS PERIOD. 



White from the Subcarboniferous strata at BurHngton, Iowa. In general 

 aspect, it is rather more nearly like that shell than the one which Meek and 

 Worthen have referred {loc. cit.) to S. planosulcata from the Keokuk lime- 

 stone of Illinois. If the species here described should be referred to any 

 described American species, it ought, I think, to be referred to 8. crasskar- 

 dinaUs White. 



Position and localitij. — Strata of the Carboniferous period : Santa Fe, 

 New Mexico ; and Rush Creek, Lake County, Colorado. 



Family TEREBEATULID^. 



Genus TEEEBEATDLA Lhwhyd, 1G9S. 



Subgenus DIELASMA King, 1859. 



Terebratula (Dielasma) bovidens Morton. 



Plate XI, fig. 10 a, J), and c. 



Terehratula hovidens Morton, 1830, Am. Jour. Sci. & Arts, xxix, 150. 

 Terebratula millepunctata Ilall, 1S5S, Pacific Eailroad Survej^s, iii, 101. 

 Terebratula geniculosa McGhesiiey, 1S60, Descr. New Pal. Fossils, 82. 

 Terebratula boviclens Meek, 1872, TJ. S. Geol. Surv. Nebraska, 187. 

 Dielasma ? hovidens White, 1874, Exp. & Surv. west lOOtli Merid., Prelim. Rep. Invert. 

 Foss., 21. 



Shell ovate or elongate-ovate in outline ; sides behind the middle lat- 

 erally compressed, where also the shell is narrower, and its vertical diame- 

 ter greater than in front of the middle. Ventral valve strongly arcuate 

 from beak to front, the curvature being greatest behind the middle, rather 

 more capacious than the other valve ;, beak prominent, incurved, but not 

 coming quite in contact with that of the dorsal valve ; foramen moderately 

 large, not squarely truncating the beak, but opening obliquely backward ; 

 mesial sinus broad, and more or less distinct at the anterior part of the 

 valve, l)ut becoming obsolete at or behind the middle ; dental plates 

 extending bu.t little, if any, in fi-ont of the teeth, placed so near the sides of 

 the beak that the space between them and the sides of the shell is very 

 narrow. Dorsal valve generally almost straight along the median line from 

 the front margin to a little behind tlie middle, from which part it gently 

 curves to the beak ; gently and somewhat unifoniily convex from side to 



