298 



PHYLTJM ECHINODERMATA. 



Fam. 1. Ichthyoerinidae. With characters of order. Ichthyocrinus 

 Conrad, Lccanocrinus Hall, Taxocrinus Forbes (Fig. 203), Forbesiocrinus 

 de Kon. 



The following genera are allied here : 



Marsupites Mant. (Fig. 204), Upper Cretaceous of Europe and Asia. 

 Calyx dicyclic, large, unstalked, composed of large thin plates, viz. 

 central (? centrodorsal), 5 infrabasals, 5 basals and 5 radials (Fig. 191). 

 Interradials and anals absent. Arms entirely free, branched, uniserial 

 with dorsal canal. 



Uintacrinus Grinnell. Calyx pseudo-monocyclic, symmetrically penta- 

 merous, unstalked, composed of thin plates. Infrabasals sometimes 

 preserved, bxit usually atrophied. 5 basals enclosing a small pentagonal 

 centrodorsal, 5 radials, and 5x2 primibrachs. The axillary primibrach 

 carries two rows of secundibrachs which gradually pass into the arms. 

 Intersecundibrachs, usually 2, may rise to 8. Arms long, thin, uniserial, 

 with numerous pinnules, connected over the calyx wall by large inter- 

 brachials. Upper Cretaceous of Kansas and Westphalia. 

 Order 5. AKTICULATA J. Mull. (Neocrinoidea P. H. Carp. Canalic-ulata 



Chapman.) 



Calyx-cover membranous, or with usually flat, loose plates. Ambula- 

 cral furrows and mouth open. Orals are present in the young state, and 

 sometimes in the adult. Calyx regular (all interradii alike), pseudo- 

 monocyclic (i.e. the infrabasals usually not separate, 

 but atrophied or fused with the top stem- joint) ; 5 

 basals sometimes not visible externally ; radials laterally 

 in contact except in Thaumatocrinus. 5x2 primibra- 

 chials. Anal plates always absent. Interradials rarely 

 present. Arms branched or unbranched. Stalk pro- 

 bably always present in the young, but absent in some 

 adults. Basals, radials and brachials perforated by 

 dorsal canals. Arms (with one exception) uniserial or 

 alternate, with pinnules. 



Trias to present time. The group includes all living, 

 tertiary, and mesozoic Crinoids except Marsupites and 

 Uintacrinus. They are mainly characterized by the 

 open mouth and ambulacral grooves and by the dorsal 

 canal in the arm plates. 



Fam. 1. Encrinidae. Calyx dicyclic, 5 small infra- 

 basals stuck on to the top stem- joint, 5 basals, 5 

 radials, interradials absent. Calyx cover arched and 

 plated. Arms divide once or twice, close together, 

 biserial or alternate. Trias. Encrinus Miller (Fig. 205). 

 Fam. 2. Apiocrinidae. Calyx regular, composed of 

 very thick plates, 5 large basals, primibrachs or 

 2 x 5, and sometimes secundibrachs. Pseudomono- 

 cyclic, the infrabasals being fused with the centro- 

 dorsal. Interradials are sometimes present, but above 

 the radials. Calyx cover plated. Arms branched with 

 long pinnules. Stalk long, circular, rarely pentagonal, without cirri ofteu 

 much expanded near the calyx. Jura, Chalk, present day. Apiocrinus 

 Miller, f ; Guettardocrinus d'Orb., f ; Millericrinus d'Orb., f ; Acrochordo- 

 crinus Trautschold, f ; Calamocrinus A. Ag.* recent, Galapagos Island. 



* A. Agassiz, Calamocrinus diomedae, Mem. Museum Comp. Zoology, 1892. 



FIG. 205. Encri- 

 nus hliiformis 

 (from Clans). 



