150 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



PENTREMITES CALYCE ( n. s.). 



A specimen having many of the characters of the above species, pre- 

 sents a much greater width of body in proportion to the height. The 

 pseudambulacral fields are also broader, and do not widen towards the 

 top ; and the poral plates are a little larger. The striae of the surface are 

 more distinct, and the interradial plates are marked on the upper end by 

 several very small nodes; a character which has not been observed in 

 the P. leda. 



Geological formation and locality. In the shales of the Hamilton group: 

 Western New- York. 



PENTREMITES MAIA ( n. s.). 



Body elongate - ovata ; greatest width just above the base of the 

 pseudambulacral areas. Base small, sharply triangular near the 

 junction of the very small column. Basal plates short, forming 

 about one-third of the height below the pseudambulacral fields. 

 Radial plates narrow, elongate, forked about four-fifths of their 

 length. Interradial plates minute, quadrangular or lozenge-shaped. 

 Pseudambulacral fields narrow, widening towards the summit, 

 convex, slightly elevated above the margins of the radial plates, 

 composed of a double series of highly ornamented poral plates; 

 the plates about twelve in one-fourth of an inch. Summit openings 

 very small. 



Surface marked by fine threadlike striae parallel to the margins of 

 the plates. 



This species differs from P. leda in the character of the base, which is 

 smaller, more elongate and attenuate, and more distinctly triangular : 

 also in the pseudambulacral fields, which are composed of longer plates, 

 giving only two-thirds as many in an equal distance. 



Geological formation and locality. In shales of the Hamilton group : 

 Moscow, N.Y. 183T. 



PENTREMITES WHITEI ( n.s.). 



Body small, somewhat broadly turbinate below the base of the 

 pseudambulacral fields, constricted just above, and rounded at 

 the summit; pentalobate in a basal view. The pseudambulacral 

 fields extend a little more than half the length of the body. Base 

 small, slightly pentangular : basal plates reaching about halfway 

 to the base of the pseudambulacral fields. Radial plates deeply 

 furcate, with the pseudambulacral areas extending about two- 

 thirds their length. Interradial plates comparatively large, lozenge 

 shaped. 



The pinnules or arms are preserved on the specimen to about twice 



