CLABK.] CASSIDULUS MICROCOCCUS. 69 



tloscoUe. The oral lobes are very promiueiit and the ambulacral farrows 

 mucli contracted (PI. xxix, Fi<»-. li). 



The anal opening- is situated iu a short sulcus ou the upper surface 

 (PI. XXIX, Figs. la-Id). 



Eclated forms. — This species is separated from the preceding, with 

 which it has much in common, by its more depressed and elongated 

 form. From G. micrococcus it is separated by its sliarper a])cx, more 

 angular margin, the position of the anal opening, and the shorter pore 

 openings in the outer rows. 



Locality and geological horizon. — This species is r<>ported from the 

 Ripley grouj) (upper Cretaceous) of Alabama. No more definite state- 

 ment as to the locality is given. 



Collection. — Philadeli)hia Academy of Natural Sciences. 



CASSIDULUS MICROCOCCUS Gabb. 

 Plate XXX, Figs. la-i. 



Canifidulus vvcrococcuR Gabb, 1860. Philadelphia Acad. Nat. Sci. Prop., p. TAd. 

 Cassidnlns micrococcus Clur'k, 1891. Johns Hopkins University Circulars, No. S7, p. 7G. 



Determinative characters. —Test oval, rounded anteriorly, slightly ros- 

 trated posteriorly; upper surface convex, flattened at the apex; sides 

 equally declining. Ambulacra moderately broad; poriferous cones 

 petaloidal on dorsal surface; outer row of pores slit-like in petaloidal 

 portion. Mouth opening small, pentagonal, with floscelle. Anal ojjen- 

 ing oval, situated high on upper surface, iu long, narrow sulcus. 



Dimensions. — Length, If inches; width, IJ inches; height, f inch. 



Description. — This species has a distinctly oval form, wider posteri- 

 orly. The upper surface is elevated at the margin, but somewhat flat- 

 tened at the apex. The sides decline very nearly equally. Tlie base 

 is flattened, with a slight concavity at the mouth edges. The posterior 

 margin is truncated and slightly rostrated. 



The. ambulacral areas are ratlier 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 (PL xxx, Figs. If, Ig). The pores are slit-like in the outer rows 

 of the petaloidal portion (PI. xxx. Fig. 1/). 



The interambulacral plates are covered with minute tubercles, with 

 sunken areolas, that increase in size and number ou the base (PI. xxx. 

 Fig. K). 



The apical disk is situated slightly in front of the center of the 

 upper surface. The right anterior genital i^late, which is modified to 

 form the madreporite, is very large. The posterior genital is not de- 

 veloi^ed, or if present the suture is obscured (PI. xxx, Fig. Ih). 



The anal opeMng is oval, situated high ui)on the upper surface, in a 

 long, narrow, and deep sulcus (PI. xxx. Figs, la, Id). 



Belated forms. — A comparison of this species with Gassidulns ceqrio- 



