CRETACEOUS ECHINODERMATA. 69 



of the upper surface is forward of the center, making the anterior margin full, the posterior 

 flattened. 



The ambulacra are broad and lanceolate. They contract appreciably just above the ambi- 

 tus, giving to the poriferous zones a subpetaloidal form. The pores of the sybpetaloidal portions 

 are large and oval, those of the outer rows more elongated than those of the inner and acumi- 

 nated on their inner margins. The pores of each pair are united by a furrow. The inner por- 

 tions of the ambulacra! plates are covered with tubercles, which in the broadest portion of the 

 subpetaloidal areas reach five or six in number. Below the subpetaloidal areas the pores recede 

 from the outer margin of the plates. Those of each pair are close together, small, and nearly 

 round, and the plates also become broader. 



The interambulacral plates are large and covered with numerous, irregularly arranged tuber- 

 cles. A microscopic granulation covers the intertubercular space. 



The position of the apical system is forward of the center of the upper surface, although none 

 of the plates are preserved on the specimen examined. The peristome is small and obliquely 

 placed slightly in front of the center of the base. 



Related forms. — Under the name of B. elevatus Gabb describes a species from Peru that is not 

 unlike B. alabamensis in many particulars. B. alabamensis, however, is larger, less rounded ante- 

 riorly, and has a more depressed posterior margin. 



Locality. — Alabama. 



Geologic horizon. — Ripley formation, Upper Cretaceous. 



Collection. — Academy of Natural Sciences of Philadelphia. 



Genus ECHINOBRISSUS Breyn. 



Echinobeissus ANGUSTATUS Clark, n. sp. 



Plate XXVII, figures 2a-c. 



Determinative characters. — Test small, subovate, rounded anteriorly, subquadrate poste- 

 riorly; upper surface elevated; apex forward of the center; base concave. Ambulacra lanceo- 

 late. Peristome small, excentric; periproct small in broad shallow sulcus, placed well posteri- 

 orly. 



Dimensions. — Length 15.5 millimeters; width 14 millimeters; height 8.5 millimeters. 



Description. — This small form is subovate in ambital outline, is rounded anteriorly and 

 truncated posteriorly, giving a subquadrate effect. The upper surface is elevated and the lower 

 concave. 



The ambulacra are very indistinct on the type. The apical system is forward of the center 

 but the individual plates are indistinguishable. The peristome is small, deeply depressed and 

 excentric in front. The periproct is small in a broad shallow sulcus and placed well posteriorly. 



Locality. — Shoal Creek, Tex. 



Geologic horizon. — Buda (Shoal Creek) limestone of Washita group, Comanche series, Cre- 

 taceous. 



Collection. — Johns Hopkins University (T 3009). 



Echinobeissus expansus Clark. 

 Plate XXVIII, figures la-g. 



Echinobrissus expansus Clark, 1891, Johns Hopkins Univ. C'ire., vol.10, No. 87, p. 76. 

 Echinobrissus expansus Clark, 1893, Johns Hopkins Univ. Circ, vol 12, No. 103, p. 52. 

 Echinobrissus expansus Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 61, 62, PI. XXVI, figs. la-g. 

 Echinobrissus expansus Johnson, 1905. Acad. Nat. Sci. Philadelphia Proc. vol. 57, p. C. 



Determinative characters. — Test subquadrate, broader posteriorly, moderately convex on 

 upper surface, concave on the base. Ambulacra narrowly lanceolate. Periproct large, supra- 

 marginal; anal sulcus broad, deep, extending from near the apex to the ambitus. Peristome 

 large, situated in front of the middle of the base. 



