ca-AKKi KCHINOBKISSUS EXl'ANSUS. 61 



lacral plates covered with numerous, irregularly distributed tubercles. 

 Apical disk anteriorly situated. IMoutli opening- small, oblicine, for- 

 ward of the center. 



I)imen,sions. — Length, 2^ inches; width, L'^ inches; height, 1 inch. 



description. — The singh' im])«Tfectly i)rescrved specimen of this sjte- 

 cies, although api)arently lacking some of the chanutcristics of liotti- 

 opygus, is nevertheless referred to that genus. The test is oblong, 

 considerably depressed on the u])i)er surlace, and concave on the base. 

 The a])ex of the upper surface is forward of the center, making the an- 

 terior margin full, the posterior Hatteued (IM. xxv, Fig. Ic). 



The ambulacra! areas are broad aud lanceolate. They contract ap- 

 preciably just above the ambitus, giving' to the poriferous zones a sub- 

 petaloidal form. The pores of the subpetaloidal jtortions are large and 

 oval, those of the outer rows more elongated than th(»se of the inner 

 and acuminated on their inner margins. J'he pores of each pair are 

 united l)y a furrow. The inner portions of aml>ula('ral plates are cov- 

 ered with tubercles that in the broadest portion of the subpetaloidal 

 areas reach five or six in number (PI. xxv, Fig. Ic). Below the sub- 

 petaloidal areas the pores recede from the outer margin of the plates. 

 Those of each pair are close together, small, and nearly round. The 

 plates also become broader (PI. xxv. Fig. Id). 



The interambulacral plates are large and covered Avith numerous, 

 irregularly arranged tubercles. A microscopic granulation covers the 

 intertubercular space (PI. xxv, Fig. 1/). 



The position of the apical disk is forward of the center of the upper 

 surface, although none of the plates are preserved on the specimen ex- 

 amined. The mouth opening is small and obliquely placed slightly in 

 front of the center of the base. 



Related forms. — Gabb describes a species of Botriopygns from Peru 

 under the name of B. elcvafus that is not unlike B. alabarnensis in many 

 particulars, though the American species is larger, less rounded anteri- 

 orly, and has a more depressed posterior margin. 



Locality and tjeological horizon. — This form is from the Ripley group 

 (upper Cretaceous) of Alabama. Its exact locality is unknown. 



Collection. — Philadelphia Academy of Natural Sciences. 



ECHINOBEISSUS Breyn. 

 EcHiNOBRissu« EXPANSUS Clark. 

 Plate XXVI, Figs. la-y. 



Echhwbrissns expansua CLirk, ISiU. .Tolius Hopkins University Circulars, No. 87, p. 76. 



Determinative characters. — T(?st subquadrate, broader posteriorly, 

 moderately convex on up])er surface, concave on the V>ase. Ambulacra 

 narrowly lanceolate. Anal o]>ening large, supra nuirginal; anal sulcus 

 broad, deep, extending from near the apex to the ambitus. Mouth 

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



