DESCRIPTIONS OF THE SPECIES. 233 



contracted, and concave centrally ; section roughly decagonal, the interradial areas 

 divided bv deep grooves; periphery almost equatorial, or perhaps a little nearer the 

 summit. Basal plates small, quite hidden in a side view; basiradial sutures usually 

 plainly visible. Radial plates more or less elliptical, gently convex ; bodies reduced 

 to a minimum, and either on a level with the outer edges of the basal plates, or 

 projecting below them ; limbs forming four fifths of the calyx, horizontally truncated 

 above, narrow, and convex, and the lateral margins almost vertical ; sinuses extending 

 nearly the whole length of the calyx, and bounded almost entirely by the radial plates ; 

 lips projecting and acting as supports, on which the calyx rests when in its natural 

 position ; interradial sutures in deep but narrow depressions. Deltoid plates small 

 and triangular, with broad bases, constricted at their proximal ends, and projecting 

 above the summit. Ambulacra convex or angular, sublinear, inserted in the sinuses 

 more deeply at their proximal than at their distal ends ; ambulacral groove deeply 

 impressed in the lancet-plate, and forming the only part of the latter which is 

 exposed ; side plates elongated, subhexagonal 1 , from forty-five to fifty in number, 

 usually concealing the hydrospire-plate. Two hydrospire-folds on each side of an 

 ambulacrum ; spiracles eight, oval, chiefly excavated in the lateral margins of the 

 deltoids, having each of their inner edges obliquely raised and thickened into a small 

 border. Mouth moderately large, covered by minute angular plates. Anus transversely 

 oval, bounded distally by a boss or node, which is more prominent than on the other 

 deltoids. Ornament consisting of granules roughly arranged in longitudinal rows. 



Remarks. This is a much larger form than either of the other species which we refer 

 to Cryptoblastus, except perhaps CA projectus ; while it is also readily distinguished 

 by its sunken ambulacra and the deeply furrowed interradial sutures (PL VII. fig. 14). 



We have made no sections of the hydrospires of this species, but there are some 

 examples of it in Mr. Wachsmuth's collection which show that it has two folds on 

 each side of the ambulacrum just like G. Korxooodi (PI. VII. tigs. 1, 2). This has 

 already been mentioned by Meek and Worthen 2 , who have also seen specimens with 

 the peristome covered by a vault of small plates which extends downwards over the 

 ambulacral grooves. 



Cryptoblastus-melo is taken by Hambach 3 as the type of his second division of the 

 genus Pentremites, which has " ten distinctly visible openings," *. e. spiracles. He 

 associates with it four other species, viz. — P. Sayi, Shumard, P. JRoemeri, Shumard, 

 P. Surlingtonensis, Meek & Worthen, and P. crenulatus, Roemer. Some of these 

 species, however, do not answer to his description. There are ten spiracles in 

 Schhoilastus Sayi (PI. III. figs. 1-3) and also in that form of Pentremites Roemeri 

 which Shumard subsequently called Granatocrinus Missouriensis 4 ; but there are 



1 Owen and Shumard. 2 Proc. Acad. Nat. Sci. Philad. 1869, p. 84. 



3 Trans. St. Louis Acad. Sci. 18S4, vol. iv. no. 3, p. 545. 



* Swallow's 1st & 2nd Ann. Report Geol. Survey Missouri, 1S55, pt. 2, pi. B. fig. 2d; & Tran-. St. Louia 

 Acad. Sci. 1805, vol. ii. no. 2, p. 'Si'). 



2 h 



