308 PROCEEDINGS OF THE ACADEMY OF [1881. 



large and formed into a eup, in Corymhocrinus are very small, 

 hidden from view, and located within a deep funnel as in tlie case 

 of EucalyptQcrinus. With this genus and the allied Callicrinus, 

 Gorymbocrinus agrees in the general construction of the calyx 

 so closely, that it would be diflicult to distinguish them even gen- 

 erically, unless the vault and arms were preserved. We therefore 

 arrange Goi^ymbocrinus with the Calyptocrinidie, 



Zittel places Abacocrinus and Cromycrinus both under the 

 MelocrinidfE. 



Generic Diagnosis. — Body large, oblong. Calyx ovoid to sub- 

 globose ; composed of numerous, rather heavy and convex plates ; 

 symmetry bilateral. 



Basal disk convex, largely extending beyond the column ; com- 

 posed of four unequal plates, with a shallow concavity for the 

 reception of the column. Primary radials 3X5, the two proxi- 

 mal ones much wider than high ; the first pentagonal or hex- 

 agonal, and owing to the irregular number of basals, differing 

 somewhat in form. The second radials are hexagonal, except the 

 posterior ones which are pentagonal, smaller than the first. The 

 third irregularly pentagonal or hexagonal, depending on the rela- 

 tive size of adjoining interradials, sometimes even heptagonal. . 



Secondary radials 2 X 10; comparatively large, supporting two 

 rows of from five to six plates each, transversely arranged, alterna- 

 ting with each other, and laterally' interlocking. The first series com- 

 paratively higher, the succeeding plates gradually decreasing in 

 length but increasing in width. The two rows resemble, and 

 evidentl}' were, intei'locking arm plates, which in geological times 

 and by age became fixed and enclosed within the body ; they form 

 the two main trunks of the ray, which divides on becoming free, 

 each branch dividing several times again, but irregularly at uneven 

 intervals. 



Arms branching, long, gradually tapering, from the base up 

 composed of two rows of plates, which increase to four when the 

 bifurcation takes place. Pinnules long. 



Interradials numerous, with one plate in the first, two in the 

 second, and generally a single one in the third series, all large 

 and nearly of equal size. The fourth series has generally but one 

 plate, which is followed by several other series of smaller j^lates, 

 each composed of from two to three pieces. The first anal plate 

 is octangular, exceedingly large, larger even than the first radials. 



