1879.] NATURAL SCIENCES OF PHILADELPHIA. 261 



4. CALPIOCRINUS Angelin. 



1878. Calpiocrinus Angl. Iconogr. Crinoid., p. 12. 

 1878. ClidocMrus Angl. (syn.). Iconogr. Crinoid., p. 12. 



General form of body, with the arms closed, ovoid or pyriform. 

 Calyx bowl-shaped, composed apparently of only one ring of plates 

 below the radials; figure bilateral. This ring consists of three 

 plates, one of them small, the two larger ones equal, forming together 

 a pentagonal disc. Primary radials three by five, three times wider 

 than high, differing in size and form; the first one lunate, the 

 second quadrangular, the third and largest pentagonal. Secondary 

 radials three to four, about equal in size, except those in the 

 posterior rays whose lateral margins retreat to give space for the 

 large anal plates. The upper secondary radials support the arms, 

 some of which bifurcate, while others remain free. Arms similar 

 to those of Ichthyocrinus, their sides closely abutting, forming a 

 wall continuous with that of the calyx. Arm joints transverse, 

 quadrangular. Interradials rarely more than one, which is small, 

 wedged in between the second and third radials of adjacent rays. 

 Anals three to five, longitudinally arranged, the lower and smallest 

 which is almost triangular resting upon the basal plates, the 

 upper one extending to the top of the secondary radials. Column 

 slender, round, composed of very thin segments ; central perfora- 

 tion small, stellate. 



This genus, as described by Angelin, differs from all the rest of 

 the family in having but one ring of plates below the radials, and 

 this consists of three plates, unequal but apparently so propor- 

 tioned as to be partly radial and partly interradial in position. 

 The various figures, however, disagree in the latter respect. Such 

 a structure would seem to warrant its separation into a distinct 

 family, but as Calpiocrinus agrees in all other characters witli the 

 Ichthyocrinidae, we feel satisfied that it naturally belongs here. 

 We are inclined to think that in this genus the lower ring of plates 

 is the analogue of the underbasals, and that the true basals, if not 

 absent, are exceedingly rudimentary. We take the small triangu- 

 lar plate which has been called the first anal plate, to be the basal 

 (subradial) on the posterior side which is larger in the whole 

 family, and that the plates on the four other sides are very minute 

 or only visible in the inside. 



The presence of but one ring of plates visible below the radials, 



