ORETACEOUS TERIOD. 177 



regularl)^ but move sliortly rounded than the base ; front margin subtruncate ; 

 postero-dorsal margin nearly straiglit or slightly convex, and nearly parallel 

 with the antero-basal margin ; hinge short ; ears of about equal size, small, 

 but distinct, each forming an obtuse angle by the cardinal border, and the 

 anterior and posterior borders respectively; beaks small, distinctly defined, 

 projecting a very little over the cardinal border. Svirface marked by num- 

 erous radiating costse, which have interspaces of similar or slightly greater 

 width between them ; costse becoming smaller upon each side of the 

 umbonal region, and absent from the ears. 



The long diameter of the largest example contained in the collections 

 is about seventeen millimeters ; short diameter, fourteen millimeters. 



This beautiful and well-marked species has quite a wide geographical 

 range. It was originally discovered by Roemer in the Cretaceous strata of 

 the valley of the Guadalupe, near New Braunfels, Texas. 



Position and locality. — Strata of the Cretaceous period; southeast of Paria, 

 Utah. 



Family PTEEIID^. 



Genus INOOERAMUS Sowerby, 1814. 



Inoceramus problematicus Scblotheim, sp. 



Plate XVI, iig, 3 a. 



Mytilus prohlematicus Scblotheim, 1820, Petrefact., 312. 

 Mytilus labiatns Brongniart, 1822, Geol. ties Eavir. Paris, 215. 

 Inoceramus mytiloides Goldfuss, 1836, Petrefact. Germ., 118. 

 Inoceramus prohlemaiicus d'Orbigny, 1843, Pal. Franyaise, iii, 510. 

 Inoceramus mytiloides Ecemer, 1852, Kreidebilduiig voii Texas, 60. 



Shell oblique, elongate-ovate in marginal outline, moderately inflated 

 in its anterior and umbonal portions, but somewhat compressed posteriorly ; 

 valves subequal; left valve more capacious than the right ; umbones oblique ; 

 beaks small, pointing forward and incurved, reaching a little farther forward 

 than the anterior border ; front side broadly rounded, and nearly parallel 

 with the posterior side ; each valve, for a short distance below the beaks, 

 bent abruptly inward to the margin; 2D0stero-basal margin abruptl}^ rounded ; 

 posterior or anal side broadly rounded to the cardinal border ; hinge com- 

 paratively short. 

 12 F 





