118 PROCEEDINGS OF THE ACADEMY OF [1886. 



faces of all axillaries and succeeding plates. Ventral sac large, 

 frequently inflated. Column more or less pentagonal, its outer 

 angles placed interradiall}', the cirrhi radiall3\ 



G. Encrinid^. Dicyclic. Closely allied to the Potei'iocrinidsp. 

 but, as a rule, without anal plates. Basals with well-developed 

 axial canals proceeding to the radials. Their brachials com- 

 posed of two pieces, united by syzygy, frequently with other 

 syzygies in the higher portions of the arms. Arms biserial or 

 uniserial. 



H. AsTYLOCRiNiD^. Pedunculate in earlier life, detached from 

 the column and free-floating in the adult, but not cirihus-bearing. 

 Plates of the calyx massive, and hence the visceral cavity com- 

 paratively small. Underbasals present or absent, and also the 

 azygous piece is sometimes wanting ; while the anal plate is 

 always well developed. 



I. Catillocrinid^. Base nionoc3'clic. The pentamerous sym- 

 metry greatl}' disturbed by the unequal size of the radials. Those 

 of the antero-lateral rays much larger and supporting many more 

 arms. Arms simple; composed of single joints resting directly 

 upon the radials, with a separate socket for each arm, and a furrow 

 for each ambulacrum. Anterior ray, and both posterior rays 

 rarely with more than one arm each. There is no azygous nor 

 special anal plate, one of the posterior radials supports towards 

 the left a large ventral tube, composed of a single row of heavy 

 curved plates, longitudinally' arranged, with an open furrow along 

 their inner, i. e., ventral side. Column circular. 



J. Calceocrinid^. Base monocyclic. Calyx laterally de- 

 pressed ; hanging downward from the column ; composed of 

 three unequal basals, three arm-bearing radials, and two azygous 

 radials without arms. Basals and radials united by ligament, 

 and toward the anterior side by muscles also. In the normal 

 position of the crinoid, the basals are located posteriorly, 

 and the three radials at the opposite side. Anterior radial 

 smaller, compound ; composed of two pieces, which frequently 

 are separated by the overhanging sides of the two lateral radials. 

 Arms of the lateral rays more numerous and branching ; anterior 

 ray with a single arm, which sometimes dichotomizes toward the 

 upper end. Anal tube as in the Catilloci'inidee. 



