198 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



radial plates, and in having these resting against the radials ; from Glypto- 

 crinus in having infrabasals, and an anal plate in contact with the basals. 



S. A. Miller, in 1883, arranged a number of species under a proposed 

 genus Gaurocrimcs, which, like his Glyptocrinus, embraces a variety of forms, 

 containing species of Eeteocrinus, Glyptocrinus, and a third form, for which 

 we proposed the name Ptychocrinus, with Miller's " Gaurocrinus " splendens 

 as type. We should have preferred to accept for the latter Miller's name 

 Gaurocrinus, if he had not expressly selected as the type of his genus Hall's 

 '^ Glypto crinus'' Onealli. which is a typical Reteocrinus. 



" Glyptocrinus " priscus E. Billings, which Walter R. Billings supposed to 

 have infrabasals, and which we placed provisionally under Ptycliocrinus, has 

 since been referred by us to Periglypto crinus. 



Ptychocrinus splendens (S. A. Miller). 

 Plate XVIIL Figs, 3a, h. 



1883. Gaurocrinus splendens — S. A. Millee; Jourii. Cincin. Soc. Nat. Hist., Vol. YI., p. 230, Plate 11, 



Pig. 3. ^ 

 1885. Ttychocrinus splendens — W. and Sp. ; Revision Palseocr. Part TIL, p. 101. 

 1889. Gaurocrinus splendens — S. A. Miller; N. Amer. Geol, and Palseont., p. 247. 



Calyx elongate, obconical ; cross-section pentangular with concave sides. 

 The plates of the rays folded along the median line, so as to form broad, 

 rounded ridges, from which branches proceed to the basals, meeting there 

 smaller ridges from the infrabasals. Surface of plates studded with rather 

 conspicuous, elongate tubercles, of which a transverse one passes over the 

 suture of two adjoining radials without touching the radial ridges. The first 

 interbrachials have seven tubercles, a central one surrounded by six others ; 

 the latter occupying the outer margins, resting in part upon adjoining plates. 

 The higher interbrachials have only a central tubercle. 



Infrabasals small, only their extreme upper points visible in a side view. 

 Basals large, higher than wide ; the posterior one broadly truncated. Eadials 

 a little larger than the basals, about as long as wide. First costals some- 

 what longer than wide, and hexagonal ; the upper angles of the axillaries not 

 truncated, the interdistichals not touching them. Distichals twelve to four- 

 teen, of which the three to four lower ones take part in the calyx, the 

 succeeding ones being free arm plates ; the upper one gives off two arms, 

 which remain simple. Arms delicate, gradually tapering to a slender point ; 

 composed of a single series of rather long, wedgeform joints. Pinnules 



