60 MESOZOIC ECHINODERMATA OF THE UNITED l^TATES. [bill. 97.1 



Ainbulacral areas narrow, unigeminal; botli areas covered with minute 

 tubercles. 



Moutli opening large, elliptical, oblique. Anal opening oval, sui^ra- 

 marginal. 



Dimensions. — Length, 1^ inches j height, % inch. 



Description. — The two specimens originally described by Hall, in the 

 Mexican Boundary Survey Eeports, are the only representatives of this 

 interesting species that have been examined by the writer. The test 

 is regular and symmetrical, slightly pentagonal in outline, enlarged 

 an teri orally, contracted posteriorly. The upper surface is convex, 

 though somewhat flattened at the summit. The sides are inflated, the 

 base flattened and slightly depressed in the vicinity of the mouth open- 

 ing (PI. XXIV, Figs Ic, Id). 



The ambulacra! areas are narrow and lanceolate; the poriferous 

 zones straight and depressed, the pores small, oval, and unigeminal 

 (PI. XXIV, Fig. If). The interambulacral areas are broad and less ele- 

 vated than the ambulacral. Both the ambulacra and interambulacra 

 support numerous small tubercles, that are larger and more distinct 

 on the lower than the upper surface. Fine microscopic granules are 

 disseminated between the tubercles (PI. xxiv. Figs, le., \g). 



The mouth opening is large, elliptical, and obliquely situated slightly 

 in front of the center of the base. The anal opening is oval and placed 

 nearly in the center of the posterior margin. The apical disk is small, 

 composed of four ovarial plates, the large right anterolateral modified 

 to form the madreporite. The five small ocular plates are firmly wedged 

 between the ovarial plates (PI. xxiv, Fig. Ih). 



Related forms. — The species just described is the only representative 

 of this genus reported from American strata, and both in form and 

 structural features admits of a ready separation from all European 

 species. It presents some points of similarity with Pyrina DesmouUnsii 

 D'Archiac, but is broader posteriorly and less elevated. 



Locality and geological horizon. — Pyrina Parryi Hall is from the 

 Washita formation of the Comanche series (lower Cretaceous), and in 

 vol. I of the United States and Mexican Boundary Survey Eeports is 

 reported from Leon Springs, El Paso Eoad, Texas. 



Collection. — U. S. National Mu'seum. 



BOTEIOPYGUS D'Orbigny. 



BOTRIOPYGUS ALABAMENSIS Clark. 



Plate XXV, Figs. la-f. 



Botriopygus alahamiensis Clark, 1891. Johns Hopkins Uuiversitj' Circulars, No. 87, 

 p. 76. 



Determinative characters. — Test oblong; more or less depressed on 

 upper surface, highest anteriorly; under surface concave. Ambulacra 

 broad, lanceolate; poriferous zones subpetaloidal above. Interambu- 



