400 PALEONTOLOGY OF ILLINOIS. 



GENUS CYATHOCRIXITES, Miller. 



Cyathocrinites, MILLER, 1821. Nat. Hist. Crinoidea. p. 85 ; Queimt, 1835, "Wegm. Arch, pp. 11, 89.* 



A s properly restricted to true typical species, such as the C. planus, 

 Miller, and C. mammillaris, C. calcaratus and C. bursa, Phillips, the 

 genus Cyathocrinitcs includes forms with a more or less globose (or 

 perhaps rarely obconic) body, composed of thin pieces, which below the 

 vault consist of the basal, subradial and first radial plates, and but a 

 single anal piece that can be properly regarded as forming a part of 

 the walls of the body below the top of the first radials. Of true inter- 

 radials there are apparently none. The base consists of five pieces, all 

 normally of the same form, and alternating with these there are five 

 generally larger subradials, one of which, on the anal side, differs in 

 form from the others, being truncated above for the support of the only 

 anal piece inserted between two of the first radials. The five first radial 

 pieces are comparatively large, and alternate with the subradials all 

 around. 



The succeeding radials are all small, more or less rounded, or some- 

 times angular, and always free, or form no part of the walls of the 

 body, those of each ray being distinctly separated by more or less wide 

 interradial spaces. The number of these free pieces varies from two to 

 some six or seven to the ray, the number being generally different in 

 the different rays of the same individual. The arms are slender, more 

 or less bifurcating and rounded, or sometimes angular, and always com- 

 posed of a single series of pieces provided with a deep ambulacra! 

 furrow along the ventral or inner side, and apparently without ten- 

 tacula (pinnule) along its margins. The column is generally, if not 

 always round, and pierced by a small canal, and not divisible into five 

 sections longitudinally. 



The vault in this genus is always much depressed, never being 

 extended upward in the form of a large poriferous trunk, or so-called 

 proboscis, as we see in the typical forms of Poteriocrinus. It is very 

 rarely preserved in the specimens as usually found, but according to 

 PHILLIPS and AUSTIN'S figures of C. planus it would appear to be pro- 

 vided with a lateral proboscis, or more properly, as we think, anal 

 tube, and an apparent central oral aperture. From specimens of C. 

 malvcweus and C. lowemis, however, which we have had an oppor- 

 tunity to examine in Mr. WACHSMUTH'S collection, and have described 

 in another place, we are satisfied that in these species at least, which 

 appear to be typical examples of the genus, the apparent central open- 

 ing is closed by vault pieces in perfect specimens. These central pieces, 



* For a complete synonymy of this gen no, see Vol. II. p. 175 of these Reports. 



