198 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
radial plates, and in having these resting against the radials; from Glypto- 
erinus in having infrabasals, and an anal plate in contact with the basals. 
S. A. Miller, in 1885, arranged a number of species under a proposed 
genus Gaurocrinus, which, like his Glyptocrinus, embraces a variety of forms, 
containing species of Leteocrinus, 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 
** Glyptocrinus”’ Onealli, which is a typical Feteocrinus. 
“ Glyptocrinus” priscus KE. Billings, which Walter R. Billings supposed to 
have infrabasals, and which we placed provisionally under Ptychocrinus, has 
since been referred by us to Periglyptocrinus. 
Ptychocrinus splendens (S. A. Mitrer). 
Plate X VIII, Figs. Sa, b. 
1883. Gaurocrinus splendens —S. A. Mit1eR; Journ. Cincin. Soc. Nat. Hist., Vol. VI., p. 230, Plate 11, 
Fig. 3. 
1885. Ptychocrinus splendens — W. and Sr.; Revision Paleocr. Part IIL., p. 101. 
1889. Guaurocrinus splendens —S. A. MitteR; N. Amer. Geol. and Paleont., 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. Radials 
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 
