CRETACEOUS ECHINODERMATA. 75 



row are oval, those of the outer elongated, and each pair united by a shallow furrow. Toward 

 the margin the pores are smaller and placed near together and so continue until near the peris- 

 tome, where the poriferous zones suddenly expand. At this point the pores increase in size and 

 distance from one another. Between the oral lobes the poriferous zones again suddenly 

 contract. 



The interanibulacra are of unequal width; the anterior pair are the narrowest; the three 

 posterior are of about equal width and nearly one-half wider than the anterior. The surface of 

 the plates is irregularly covered with numerous small perforated tubercles, with sunken areolas 

 between which are numerous microscopic granules. 



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

 fifth genital is obsolete. The large right anterolateral genital plate, the madreporite, extends 

 across the disk, forming a large portion of the center of that body. 



The peristome is large, pentagonal, and slightly nearer the anterior margin. It is sur- 

 rounded by five prominent lobes that project over the oral opening. The ambulacra are con- 

 tracted between the lobes and expand beyond them into wide phylloidal areas, producing a 

 peculiar, somewhat star shaped form that has been termed the floscelle. 



The periproct is small, circular, and supramarginal, and is situated in a short, narrow sulcus. 



Related forms. — Cassidulus florealis is allied to ft sequoreus, although the latter is more 

 depressed and more elongated. In some points it is similar to ft subconicus but has a less 

 sharply denned pentagonal outline, a differently situated periproct, and less elongated pores 

 in the outer rows of the petaloidal areas. 



Localities. — Chesapeake & Delaware Canal, Del. (type) ; Uniontown, Ala. 



Geologic horizon. — Matawan formation, Delaware, and Selma chalk, Alabama, of the 

 Upper Cretaceous. 



Collection. — Academy of Natural Sciences of Philadelphia (149.5). 



Cassidulus xquoreus Morton. 

 Plate XXX, figures 2a-i. 

 Cassidulus xquoreus Morton, 1834, Synopsis Organic Remains Cretaceous, p. 76, PL III, fig. 14. 

 Cassidulus xquoreus Desmoulins, 1837, Etudes sur les echinides, p. 146. 

 Cassidulus xquoreus Lamarck, 1S40, Hist. Nat., vol. 3, p. 341. 

 Cassidulus sequoreus Agssiz and Desor, 1847, Catalogue raisonne, p. 141. 

 Cassidulus xquoreus D'Orbigny, 1847, Prodrome, vol. 2, p. 271. 

 Cassidulus sequoreus Bronn, 1848, Index palseontologicus, vol. 1, p. 244. 



Cassidulus xquoreus D'Orbigny, 1853-60, Paleontologie francaise, vol. 6, p. 329, PL CMXXVI, figs. 6-12. 

 Cassidulus xquoreus Desor, 1858, Synopsis des echinides fossiles, p. 290. 

 Cassidulus xquoreum Gabb, 1859, Cat. Invert. Fossils Cretaceous, p. IS. 

 Cassidulus xquoreus Meek, 1S64, Smithsonian Misc. Coll., vol. 7 (177), p. 2. 

 Cassidulus xquoreus Conrad, 1868, Geology of New Jersey, App. A, p. 722. 

 Cassidulus xquoreus Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 76. 

 Cassidulus xquoreus Clark, 1S93, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 52. 

 Cassidulus xquoreus Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 68, 69, PL XXIX, figs. la-i. 

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



Cassidulus xquoreus Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 293-294, PL 

 XII, figs. .5-12. 



Determinative characters. — Test subpentagonal, depressed; upper surface convex; under 

 surface concave, slightly rostrated posteriorly; apex forward of the center. Ambulacra narrow; 

 poriferous zones petaloidal on the upper surface; contracted above the margin and expanded 

 again on the lower surface, much narrowed at the peristome. Interanibulacra wide, covered 

 with small perforated tubercles. Apical system small, situated forward of the center. Peris- 

 tome smaU, with floscelle. Periproct supramarginal, in short sulcus. 



Dimensions. — Typical form: Length 31.25 millimeters; width 28.12 millimeters; height 

 15.6 millimeters. 



Description. — This typical Cassidulus, early recognized as such by Morton, has a depressed 

 test, subpentagonal in outline. It is longer 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 somewhat anterior to the center. 



