290 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



Oykena inflexa Meek. 



. Plate 10, figs. 7 a and &. 

 CorUcula ( Veloritina) inflexa Meek, 1871, An. Eep. U. S. Geol. Suiv. Terr, for 1872, p. 493. 



The figures of this species on plate 10 were drawn from Mr. Meek's 

 types, and the following is a copy of his original description: 



" Shell longitudinally ovate, a little less than two-thirds as high as 

 long, moderately convex; posterior extremity rather narrowly rounded, 

 or apparently sometimes faintly truncated; anterior very short, sub- 

 truncated, or more or less sinuous in outline, just in advance of the 

 beaks, on the abrupt forward slope above, and rather abruptly rounded 

 below; basal margin semiovate or semielliptic; dorsal margins inflected 

 and forming a long convex slope from the umboual region i)Osteriorly; 

 beaks rather depressed, oblique, incurved, and placed near the anterior 

 end;, umbonal slopes not prominently rounded; surface merely showing 

 fine, rather obscure marks of growth; anterior muscular impression 

 rather strongly defined and obliquely ovate; posterior muscular im- 

 pression larger and obscure ; pallial line showing a deep, angular, ascend- 

 ing sinus ; posterior lateral teeth of hinge very long, hnear, and nearly 

 or quite smooth ; anterior short; cardinal teeth very obhque. 

 ■ "Length of a specimen a little under medium size, 1.35 inches; height, 

 0.39 inch ; convexity, 0.68 inch. 



'■^Locality and position. — IsTear Missouri Eiver, below Gallatin City, 

 Mont., where it occurs associated with Trigonia^ Inoceramus, Cardium 

 Ostrea, and other marine Cretaceous fossils." 



Mr. Meek referred this shell to the genus CorMcula and his subgenus 

 Veloritina. It is almost certainly not Corhicula^ as that genus is usually 

 restricted, because its lateral teeth are not transversely striated, and its 

 pallial sinus is very different. As remarked in connection with the 

 description of the preceding species, I refer such shells as that and this 

 one to Cyrena, if found associated with marine Cretaceous species and 

 the lateral teeth show no striation. The character of the lateral sinus, 

 however, as pointed out by Mr. Meek, is very Uke that of the Veneridw, 

 and not like that of either CorMcula or Cyrena, and it is Mkely that this 

 shell does not properly belong to either of those genera. But until we 

 can obtain specimens which show clearly the character of all parts of 

 the hinge, I prefer to refer such forms as this to Cyrena, as before stated. 



Genus COEBTJLA Brugui^re. 



COEBULA NEMATOPHORA Meek. 



Plate 3, figs. 4 a, l, c, and d. 



Corbula nmiatopliora Meek, 1873, An. Eep. U. S. Geol. Surv. Terr, for 1872, p. 496. 

 Corhiila nematojjhora White, 1876, Expl. & Surv. West of lOOth Merid., vol. iv, p. 188, 

 pi. xvii, fig. 7. 



" Shell of about medium size, ovate-subtrigonal, nearly equi valve and 

 moderately convex, with height equaling two-thirds the length ; anterior 

 outline rounded; base semi-ovate; posterior extremity somewhat pro- 

 duced and subangular or minutely truncated in outline below ; dorsal 

 outline sloping from the beaks, the anterior slope being more abrupt and 

 slightly concave in outUne above, and the posterior longer and nearly 

 straight, with a greater obhquity ; posterior umbonal slopes more or less 

 angular in each valve, from the beak to the posterior basal extremity ; 

 beaks rather prominent, and. placed about one-third the length of the 



