INVERTEBRATES. 215 



We know but the single typical species, which is from the Subcarboniferous 

 series. 



Ccelocrinus concavus, M. and W. 



PI. 15, Pig. 10 a, 10 6, 10 c. 



Actinocrinus (Amphoracrinus ?) concavus, Meek and Worthen, June, 1861. Proceed. 

 Acad. Nat. Sci., Philad., p. 132. 



Actinocrinus (Sphxrocrinus) concavus, M. and W., Aug., 1865. lb., p. 154. 



Actinocrinus (Ccelocrinus) concavus, M. and W., Dec, 1865. lb., p. 273. 



££■ Body small, subglobose, broader than high, a 



oOpP^ little oblique; summit nearly flat; under side 



SO/oPrt rounded and distinctly concave ; sides rising ver- 



'MOYv'-'b^ Really, or nearly so. Surface smooth, or sub- 



0% AVOo granulose. Base small, concave, and entirely in- 



n eluded within the concavity of the under side. 



c lNlturai C sf Z e a .r s ' First radial plates comparatively large, convex, 



stmoture of thTbody and curving under so as to form a part of the 



out to the brachial • i i i pit i i -i 



pieces inclusive, with concavity below; two- 01 them heptagonal and 



the position of the J ' . 



opening at te a. al anai three hexagonal. Second radial pieces wanting 

 in two of the rays (of the specimen before us) ; in the 

 others small, wider than long, and quadrangular in form. 

 Third radial pieces smaller than the second (in three of 

 the rays), pentagonal in form, and each supporting upon 

 their superior sloping sides the first brachial pieces, which 

 form a part of the walls of the body. First interradial 

 pieces comparatively large, or about one-half the size of 

 the first radial plates, nine sided, the superior sloping sides 

 of each supporting one side of two of the brachial pieces, 

 while two very small pieces rest upon the middle of the sum- 

 mit, and connect with the vault above, and with the brachial 

 * ces on each side. First anal piece a little larger than the 

 n ials, heptagonal in form, and supporting in the next 



