5 



tremely short oblique sides below. Pseudo-ambulacral areas 

 broad, nearly plane, and extending only about half way from 

 the summit to the base, rather deeply impressed at their 

 rounded lower ends ; poral plates varying from 6 to 13. 

 Oral aperture small, pentagonal ; anal aperture large, oval ; 

 ovarian opening small, nearly round ; surface very finely 

 and beautifully striated ; striae on the sides of the radial 

 plates nearly vertical, but on the lower part they are de- 

 flected obliquely across so as to meet at an obtuse angle on 

 the centre below the ambulacral areas. Column at its junc- 

 tion with the body round, relatively very large. 



Length, one-twelfth to one-fourth of an inch. 



Locality. — Spergen Hill ; Bloomington, la. ; Alton, 111. 



This species resembles P. caryophyllatus of De Koninck, 

 (Crinoides du Terrain carbonifere de la Belgique,) but dif- 

 fers in the shorter base and peculiarity of the basal plates, 

 as well as in the interradial plates, which in our species are 

 extremely small and almost linear, the one on the anal side 

 extending into that aperture. A single individual shows a 

 nearly entire obliteration of one of the pseudo-ambulacral 

 spaces. 



Pentremites conoideus. — General form conoidal or pyra- 

 midal with the angles rounded ; base subtruncate ; apex a 

 little flattened ; plates of the base rather flattened ; radial 

 plates extremely elongated and deeply divided for the re- 

 ception of the pseudo-ambulacral areas ; interradial plates 

 deeply inserted between the radial plates, long lanceolate, 

 and very acutely pointed above ; pseudo-ambulacral spaces 

 very elongate, narrow, extending nearly to the base, with 

 sides sub-parallel, convex along the median line ; median 

 line sharply depressed ; poral plates varying with age from 

 25 to 50 ; ovarian apertures circular ; anal aperture ovate 

 and much larger than the others. Surface marked by fine, 

 closely arranged striae, which on the radial plates are paral- 

 lel to the margins till near the summit, where they are 



