160 KANSAS UNIVERSITY SCIENCE BULLETIN. 



and Hayden, by its larger size and especially the larger 

 striae, which are not strikingly prominent until 15 or 20 mm. 

 from the beak, while those of A. vmccoyi Meek and Hayden, 

 are equally distinct 3 to 5 mm. from the beak. Otherwise 

 they are very similar. The general appearance of the shell 

 is a trifle like A. occidentalifi Meek, but is at once distin- 

 guished from it by its larger ears with coarse marks and the 

 nodose character of the larger ribs. 



ALLORISMA ? ALBEQUUS, n. sp. 



Plate VII, figures 5-5c. 



Shell minute, equivalvular, subquadrilateral, benks promi- 

 nent. The anterior margin descends obliquely from the beak 

 to the anteroventral region where it is abruptly rounded. 

 Ventral margin is slightly sinuate because of the faint de- 

 pression extending obliquely backward and downward from 

 the beak. Posterior margin pretty regularly rounded, meet- 

 ing the hinge at a very oblique angle. Hinge straight, its 

 other characters unknown. The beaks project above the 

 hinge and are incurved forward. The surface was probably 

 nearly smooth, with faint undulations of growth. Two speci- 

 mens : Length, 5.5 mm., 4.5 mm, ; height, 2.25 ram., 2 mm., 

 respectively. Length of hinge, 2.75 mm. and 2 mm 



Whitehorse spring, Oklahoma ; rare. Dozier, Tex. ; com- 

 mon. 



These fossils have the general expression of the Allorismas, 

 and are provisionally referred to them until material demon- 

 strating the character of the hinge dentition can be had. 



PLEUROPHORUS? ALBEQUUS, n. sp. 



Plate VI, tigares 8-8e. 



Pleurophorus sp. Beede, Inv. Pal. Red Beds, p. 9, pi. I, fig. 4, 1902. 



Shell of medium size to rather small for this genus ; height 

 at the beak about one-third the length ; beak rather promi- 

 nent, nearly terminally located, projecting above the hinge; 

 umbonal ridge not sharply defined, but well rounded ; in front 

 of the ridge is an undefined oblique depression, frequently 

 producing a slight sinuosity in the ventral margin. Hinge 

 very slightly arcuate and long. The anterior outline slopes 

 and rounds obliquely downward, merging into the ventral 



