70 MESOZOIC ECHTNODERMATA OF THE UNITED STATES. [bull. 97. 



reus, as made also by Gabb in his original description, shows that the 

 present form is much larger and more oval, and that the anal opening is 

 situated higher and in a deeper and longer sulcus, and, furthermore, 

 that the pores of the outer row in the petaloidal portion are elongated 

 and slit-like. 



Locality and geological horizon. — This species is from the Kipley group 

 (upper Cretaceous) of Eufaula, Alabama. 



Collection. — Philadelphia Academy of I^atural Sciences. 



Oassidultts subqtjadratus Conrad. 



Plate XXXI, Figs. 1 Or-h. 



Casaiduhts suhquadrafus Conrad, 1860. Philadelphia Acad. Nat. Sci. Jonr., 2d ser., 



vol. 4, p. 291, PI. 47, Fig. 19. 

 Cassidulus suhqiiadratus Clark, 1891. Johns Hopkins University Circulars, No. 87, 



p. 76. 



Determinative cliaracters. — Test subquadrate to subpeutagonal, hemi- 

 spherical; sides equally declining, upper surface convex; lower surface 

 concave; posterior margin truncated and rostrated. Poriferous zones 

 broadly petaloidal on iipj^er two-thirds of the dorsal surface; sharply 

 contracted at lower margin of j^etaloidal areas. Mouth opening small, 

 pentagonal, with well-defined tioscelle. Apical disk large, slightly 

 anterior to the center. Anal opening round, in deBp sulcus. 



Dimensions. — Length, 2^ inches; width, 2 inches; height, 1 inch. 



Description. — This remarkably symmetrical Cassidulus has a nearly 

 hemispherical form. In outline it is nearer subpentagonal than sub- 

 quadrate, due to the rostrated character of the i)osterior luargin, which 

 is at the same time truncated. The anterior margin is rounded. The 

 lateral edges are nearly parallel, though somewhat more approximated 

 anteriorly. The aj^ex is slightly forward of the center. 



The ambulacral areas are moderately wide in the petaloidal portion, 

 narrow beyond. The poriferous zones are comi)osed in 'the petaloidal 

 portion of an inner row of small, nearly circular pores and of an outer 

 row of oblique slit like openings. The pores of each pair are united by 

 a shallow furrow (PI. xxxi. Fig. 1/). Beyond the petaloidal areas the 

 narrow plates of those portions give place to broad plates, each with a 

 pair of small, round pores in the lower and outer corner (PI. xxxi. Fig. 

 Ic). In the vicinity of the peristome the poriferous zones expand and 

 the pores increase in size, though appareutly reduced in number (PI. 

 XXXI, Fig. 1^). The last pair of plates are nmch contracted. 



The interambulacral areas are wide. The plates are covered with 

 miuute tubercles with depressed areolas, which become larger and more 

 prominent on the lower surface. 



The apical disk is large, composed of four perforated genital and five 

 ocular plates. The fifth geuital is appareutly obsolete (PI. xxxi, 

 Fig. 1/0. 



