DESCRIPTIONS OF IXVERTEBUATE FOSSILS. 57 



Nation. It was associated with Holrcfi/pus phiiKtfitst. Kroffi/rii 

 texaim, TuvriivUa s<'ri(itim-gr((niih(t(t, etc. 



The species belongs to the subgenus ^4 c/7a. 



Cardium quinordinatum, sp. nov. 



Shell of rather small size for its genus, rounded-triangular, 

 subequilateral, the anterior and posterior sides of the outline 

 slightly concave in the upper and convex in the lower part, 

 the liasal margin being evenly rounded, the part of the out- 

 line formed by the arched unibonal summit being very ob- 

 tuse; beaks subcentral, large, arched strongly, the arch rising 

 high above the hinge-line; surface ornamented with some- 

 thing like twenty broad, prominent, rounded, spinigerous 

 costse separated by narrow plain-bottomed intervals, the costal 

 spines being of the squamous type, having the form of caret- 

 shaped hoods, and being closely set in five radial ranks on 

 the same number of slightly elevated rays on each costa, the 

 rays being separated by stri?eform grooves. The intercostal 

 valleys are a little less than two-fifths as wide as the costae. 

 Of the five spinigerous rays on each costa, the middle one is 

 relatively larger and more coarsely spined than those adjacent 

 to it, the two outermost being the smallest of all. 



Measurements. — Height 21, length 19, breadth 16 mm. 



Occurrence. — There is a little doubt as to the source of 

 the two type-specimens of this species. They were, however, 

 almost certainly collected at a ledge of the Washita limestone 

 a little east of Georgetown, Texas, in association with Ostrea 

 roanokensis, Pleurotomaria robusfa, nnd ISclilooihacliia ana- 

 find. 



ROUDAIRIA DENISONENSIS, sp. UOV. 



Shell among the larger representatives of its genus, ele- 

 vated-triangular, the lateral profile of its cast approaching an 

 isosceles triangle with convex base, but the supero-posterior 

 part of that profile presenting, as in R. quadruns,* a low 



*Seo American Geologist, Vol. XIV, PI. I, fig. 14. R. quadrans should be com- 

 pared witli tlio slioll described in the writer's "Contrihution to the Invertebrate 

 Paleontology of the Texas Cretaceous," as Trii/oiiia securiforins, witli which it is 

 quite likely that it will prove to bo identical. There can be little doul)t that the 

 latter species belongs to the genus Houdairia. 



