CLARK] CASSIDULUS STANTONI. 73 



The anal opening is large, oval, and is situated at the liead of a 

 short, narroAV sulcus (PI. xxxiii, Figs. 1«, lb). 



Related forms. — Gassidulns porrectm is from its size, form, and de- 

 tails of structure readily separated from the other species of Cassidulus 

 described from the American and Enrojican Mesozoic. 



Locality and geological horizon. — Cassidvlus porrectns is from the 

 Ki]»ley group (upper Cretaceous), of lOufauhj, Alabama, in the pre- 

 liminary report, i)ubhshed in the Johns Hopkins Circulars, the writer 

 incorrectly cites Mississippi as the locality. 



Collection. — U. S. National Museum. 



Cassidulus Stantont Clark. 

 Plate XXXV, Figs. 2a-d. 



Cassidulus Sfantoni Clark, 1891. Johns Hopkins University Circnl.ars, No. 87, p. 76. 



Determinative characters. — Test small, subovate, elevated; upper 

 surface convex, lower surface concave; apex forward of the center. 

 Ambulacra very narrow. Apical disk small, forward of the center. 

 Mouth opening small, with floscelle. Anal opening high above mar- 

 gin, in long, narrow, and deep sulcus. 



Dimoisions. — Length, § inch; width, ^ inch; height, ^ inch. 



Description. — This minute Cassidulus has a subovate test, an elevated, 

 convex upper surface and a concave lower surface. It is broader pos- 

 teriorly than anteriorly, and the posterior margin is truncated. The 

 apex is situated slightly anterior to the center of the upper surface 

 (PI. XXXV, Fig. 2a). 



The ambulacral areas are very narrow. The petaloidal jiortion but 

 sliglitly exceeds the remainder in width, W'hich is nearly equal through- 

 out. The jihylloidal region is feebly outlined. 



The interambulacral areas are broad, but the poor state of preserva- 

 tion of the specimens renders it im}>ossible to determine all the details 

 of structure. 



The apical disk is small and forward of the center, but not sufficiently 

 well preserved to distinguish the individual plates. The mouth open- 

 ing is small and surrounded by a feeble tloscelle. The anal oi)ening is 

 round and situated high above the margin, at the head of a narrow, 

 deep sulcus (PI. xxxv. Figs. 2a, 2d). 



Related forms. — Cassidulus Stantoni is quite unlike any other repre- 

 sentative of this genus from American strata, and can not be readily 

 associated with any European species. 



Locality and geological horizon. — This species is from the Colorado 

 group (upper Cretaceous) of Muddy creek, Huerfano county, Colo«nlo. 



Collection. — U. S. National Museum. 



