ciARK] PYRINA I'ARRYI. 59 



cles are fouii<l in tlio broadiT ])(»rti()ii of tlic iireas, which IxM-oine re- 

 duced to four toward the apical disk :iud luouth edges (IM. win, Fig. 2e). 



The iuterambulaeral areas are about three times tlie widtli of the 

 ambuhioral at tlie ambitus. The phites are nnriow , each with a liori- 

 zoutal row of suuill tubercles, five or six in a row at the ambitus, but 

 fewer above aud below. Each tubereh^ has a small circular areola, 

 crenulated boss, and perforated manielon. The tubercles cover the 

 greater i)orti(Ui of the plates, with minute granules interspersed be- 

 tween them (PI. XXIII, Fig. 2(1). The tubercles are very much larger 

 on the lower surface, and the ditference in size shown between those of 

 the ambulacra and interambulacra on the u]»per surfacM' disa])pears. 



The apical disk is small. The five ovarial plates are all perforated; 

 the madreporite is of large size and indistinctly separated from the 

 other plates (PI. xxiii, Fig. 2/'). 



The mouth opening is small, with slight incisions that give a decagonal 

 margin. The large oval anal opening extends from the vicinity of the 

 mouth edges to the ambitus (PI. xxiii, Fig. 2h). 



Belated forms. — Cotteau has recently described, under the name of 

 H. Castilloi, a new species of Holectypus from Mexico that is not unlike 

 certain individuals of H. planatns examined by th'e writer. As a sulfi- 

 cient number of intermediate forms has been found to connect all the 

 specimens examined with the type form described by Koemer, no at- 

 tempt has been made to establish new species, H. planus described by 

 Giebel is considei»ed such a variation. 



Locality and geological horizon. — This widely distributed form is from 

 the Washita formation of the Comanche series (lower Cretaceous) of 

 Texas. It has been found at Austin, F'redericksburg, and elsewhere. 



Collections. — U. S. National Museum; Philadelphia Academy of Natu- 

 ral Sciences; Boston Society of Natural History; Texas Geological 

 Survey; Prof. Eobt. T. Hill. 



CASSIDUIilD^ Agassiz. 



Test circular, oval or subpentagonal. Ambulacra simple or peta- 

 loid, generally similar. Mouth opening central or subcentral, generally 

 with a pentapetaloid floscelle. Anal opening excentric. 



PYRINA Desmoulins emend, de Loriol. 



Pyrina Parryi Hall. 



Plate XXIV, Figs. la-J:. 



Pyrina Parryi Hall, 1857. U. S. and Mox. Bouinl. Surv. ]{('])1., vol. 1, pt. 2, p. 144, Fi. 1, 



Fig. 1-lrf. 

 Pyrina Parryi Gabb, 1859. Cat. Invert. Fosfsils Cretacoons, j). IJ). , 



Pyrina Parryi Meek, 1864. Smith. Misc. Coll., vol. 7 (177), p. 2. 

 Pyrina Parryi Clark, 1891. Johns Hopkins University Circulars, No. 87, p. 7(5. 



Determinative characters. — Test subpentagonal, broader anteriorly 

 than posteriorly, inflated at the sides, flattened above and below. 



