.156 GEOLOGY AND PALEONTOLOGY. 



than at the ventral or basal end, which is turned downwards at an obtuse angle ; somewhat 



foliaceous externally ; muscular impression placed very near the base. 



This species approximates 0. Leymerii, Desh. It was first discovered by Lyell in North 



Carolina, associated with Belemnites mucrcmatus and Gryphcea vesicularis. This group appears 



to represent the age of the Gryphcea and Exogyra beds of New Jersey. 



Locality. — Western Texas. 



OSTREA BELLA. 



Plate X, Figure 4, a, h. 



Oblong-ovate, slightly curved ; lower valve ventricose, undulated, with somewhat interrupted, 

 radiating ribs, crossed by remote squamose concentric lines ; beak produced ; lesser valve flat, 

 concave towards the base, marked by minute, obsolete, radiating lines. 



Locality. — Western Texas. 



OSTREA LUGUBRIS. 



Plate X, Figure 5. 



Suboval ; superior valve flat ; inferior valve slightly ventricose, showing a mark of attach- 

 ment on the umbo ; ribs radiating, prominent, rugose, disappearing on the umbo. A small 

 species, constant in character, and easily recognized. 



Locality. — East of Ked river, (Canadian,) New Mexico, Santa Fe road. 



OSTREA CARINATA. 



Plate X, Figure 6. 



Ostrea carinata, Lam. An. sans vert, Desh. ed. vol. VII, p. 240. 

 Ostrea carinata, Eoemer, Kreid. von Texas, p. 75, pi. IX, fig. 5. 



Subequivalve, elongated, arched, compressed, eared anteriorly, regularly plicated ; folds 

 equal, acute, carinated, diverging from a flattened surface on the back, geniculated at the angle 

 and vertical on the sides, which are flattened. 



I have not seen good specimens of this shell, and refer it to carinata chiefly on the authority 

 of Eoemer. 



Localities. — Turkey creek, Las Minas ; New Braunfels. 



OSTREA VELLICATA. 



Plate XI, Figure 2, a, b. 



Subovate, inferior valve convex, with very irregular, laminated, concentric lines, imbricated ; 

 surface as if pinched into cavities in places ; beak subrostrated, thick ; margins of the lower 

 valve thickened, muscular impression comparatively near the base ; hinge area broad. 



I have seen but one valve of this species. 



Locality. — Rio Grande, between El Paso and Frontera. 



OSTREA ROBUST A. 



Plate XI, Figure 8, a, b. 



Elevated, subfalcate, thick ; inferior valve convex ; superior valve flattened, with rather 

 distant subimbricated laminte ; apex truncated. 



