68 MESOZOIC ECHINODERMATA OF THE UNITED STATES, [bull. 97. 



Cassidulus ^quoreus Morton. 



Plate XXIX, Figs. la-i. 



Cassidulus crquorcus Morton, 1834. Synop. Organ. Kemains, Cretaceous, p. 76, PI. 3, Fig. 



14. 

 Cassidulus wquoreus Desnioulins, 1837. Etudes sur les Echiuides, i>. 146. 

 Cassidulus wquoreus Agassiz and Desor, 1847. Cat. rais., p. 141. 

 Cassidulus wquorvus d'Orbiguy, 1847. Prodrome, vol. 2, p. 271. 

 Cassidulus lequoreus Broun, 1848. Index Pal., vol. 1, p. 244. 

 Cassidulus wquoreus d'Orbigny, 1853-'60. PaMont. franyaise, vol. 6, p. 329, PI. 926, Fig. 



6-12. 

 Cassidulus wquoreus Desor, 1858. Synop. des Echinides fossiles, p. 290. 

 Cassidulus wquorum Gabb, 1859. Cat. Invert. Fossils, Cretaceous, p. 18. 

 Cassidulus wquoreus Meek, 1864. Smith Misc. Coll., vol. 7 (177), j>. 2. 

 Cassidulus wquoreus Conrad, 1868. Geol. of New Jersey, App., p. 722. 

 Cassidulus wquoreus Clark, 1891. Johns Hopkins University Circulars, No. 87, p. 76. 



Determinative characters. — Test subpentagonal, depressed ; upper sur- 

 face convex; under surface concave, slightly rostrated posteriorly; 

 apex forward of tlie center. Ambulacra narrow ; poriferous zones peta- 

 loidal on the upper surface; contracted above the margin and expanded 

 again on the lower surface, much narrowed at the peristome. Inter- 

 ambulacra wide, covered with small perforated tubercles. Apical disk 

 small, situated forward of the center. Mouth opening small, Avith flos- 

 celle. Anal opening supramarginal, in short sulcus. 



Bimensions. — Length, 1^ inches; width, 1^ inches; height, | inch. 



Description. — This typical Cassidulus, early recognized as such by 

 Dr. Morton, has a depressed test, subpentagonal in outline. It is 

 louger in the anteroposterior diameter than the lateral. The upper 

 surface is convex, with sharp marginal edges, while the lower surface 

 is flat, with a slight concavity toward the center. The apex is some- 

 what anterior to the center. 



The ambulacral areas are narrow. The poriferous zones are unigem- 

 inal, the pores of the upper part of the dorsal surface arranged in i^eta- 

 loidal form. At a point varying in the different areas from one- 

 quarter to one-third of the distance from the margin to the apical disk, 

 the zones are contracted and continue as narrow bands over the mar- 

 gin and to the vicinity of the peristome, where they broaden again i)er- 

 ceptibly, becoming finally much contracted at the margin of the oral 

 opening (PI. xxix, Fig. le). The i)ores are distinct in the petaloidal 

 portion (PI. xxix. Fig. 1/) and in the broadened area near the peri- 

 stome (PI. xxix, Fig. If/), but in the intermediate contracted portion 

 are small and indistinct. The interambulacral areas are broad, and 

 covered by small perforated tubercles with sunken areolas. 



The apical disk is composed of four perforated genital and five small 

 ocular j)lates. As explained under the previous species, the fifth geni- 

 tal is obsolete (PI. xxix. Fig. lli). 



The mouth opening is pentagonal and surrounded by a well-develoijed 



