76 MESOZOIC AND CENOZOIC ECHINODEKMATA OF THE UNITED STATES. 



The ambulacra are narrow. The poriferous zones are uniserial, the pores of the upper part 

 of the aboral surface arranged in petaloidal form. At a point varying in the different areas from 

 one-quarter to one-third of the distance from the margin to the apical system the zones are con- 

 tracted and continue as narrow bands over the margin and to the vicinity of the peristome, where 

 they broaden again perceptibly, becoming finally much contracted at the margin of the oral 

 opening. The pores are distinct in the petaloidal portion and in the broadened area near the 

 peristome but in the intermediate contracted portion are small and indistinct. The interam- 

 bulacra are broad and covered by small perforated tubercles with sunken areolas. 



The apical system is composed of four perforated genital and five small ocular plates. As 

 explained under the previous species, the fifth genitalis obsolete. 



The peristome is pentagonal and surrounded by a well-developed floscelle. The oral lobes 

 are very prominent and the arnbulacral furrows much contracted. 



The periproct is situated in a short sulcus on the upper surface. 



Related forms. — This species is separated from C.florealis by its more depressed and elon- 

 gated form. From 0. micrococcus it is separated by its sharper apex, more angular margin, the 

 position of its periproct, and the shorter pore openings in its outer rows. 



Localities. — Prairie Bluff, Ala. (type) ; bluff east of Atlantic Highlands, N. J. 



Geologic horizon. — Navesink marl of Monmouth group, New Jersey, and Ripley formation, 

 Alabama; Upper Cretaceous. 



Collection. — Academy of Natural Sciences of Philadelphia (1475). 



Cassidulus micrococcus Gabb. 



Plate XXXI, figures la-i. 



Cassidulus micrococcus Gabb, 1860, Acad. Nat. Sci. Philadelphia Proc, p. 519. 

 Cassidulus micrococcus Clark, 1891, Johns Hopkins Univ. Che, vol. 10, No. 87, p. 76. 

 Cassidulus micrococcus Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 52. 

 Cassidulus micrococcus Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 69, 70, PI. XXX, figs. la-i. 

 Cassidulus micrococcus Johnson, 1905, Acad. Nat. Sci. Philadelphia. Proc, vol. 57, p. 7. 



Determinative characters. — Test oval, rounded anteriorly, slightly rostrated posteriorly; 

 upper surface convex, flattened at the apex; sides equally declining. Ambulacra moderately 

 broad; poriferous cones petaloidal on dorsal surface; outer row of pores slitlike in petaloidal 

 portion. Peristome small, pentagonal, with floscelle. Periproct oval, situated high on upper 

 surface, in long, narrow sulcus. 



Dimensions. — Length 45 millimeters; width 42 mUlimeters ; height 21.5 millimeters. 



Description. — This species has a distinctly oval form, wider posteriorly. The upper surface 

 is elevated at the margin but somewhat flattened at the apex. The sides decline very nearly 

 equally. The base is flattened, with a slight concavity at the peristome. The posterior margin 

 is truncated and slightly rostrated. 



The ambulacra are rather broad, contracted about one-quarter of the distance from the 

 ambitus to the apex, and narrowed nearly to the peristome, where they are again broadened to 

 form indistinct phylloidal areas. The pores are slitlike in the outer rows of the petaloidal 

 portion. 



The interambulacral plates are covered with minute tubercles, with sunken areolas, that 

 increase in size and number of the oral surface. 



The apical system is situated slightly in front of the upper surface, in a long, narrow, and 

 deep sulcus. 



Belated forms. — A comparison of this species with Cassidulus sequoreus, as made also by Gabb 

 in his original description, shows that it is much larger and more oval, and that its periproct is 

 situated higher and in a deeper and longer sulcus, and, furthermore, that the pores of the outer 

 row in its petaloidal portion are elongated and slitlike. 



Locality. — Eufaula, Ala. 



Geologic horizon. — Ripley formation, Upper Cretaceous. 



Collection. — Academy of Natural Sciences of Philadelphia (1480). 



