ECHINODERMATA—CRINOIDEA. 497 



5f. First anal plate hexagonal, followed by two interbrachials 

 without a second anal. Arms branching from two main 

 trunks by alternate bifurcation. Basals three and equal. .9*. 



9*. Anus at end of a tube 8''''. 



2>^^ . Calyx lobed ; interradial spaces depressed t^^. 



t^\ Arms given off from alternate sides of tubular 

 extensions of the calyx.. ..XXXVII. Steganocrinus. 

 e^^. Arms rarely bifurcating. Anal tube long and cen- 

 tral XXXIII. Actinocrinus. 



^'^ . Arms generally bifurcating. Anal tube short and 



excentric XXXV. Amphoracrinus. 



V . Calyx not lobed ; arms about equidistant, given off in 

 a ring around the calyx. Anal tube long and central. 



f^^. Arms directed upward XXXIV. Cactocrinus. 



V^. Arms directed outward below, incorporated into 

 the calyx and forming a broad rim. 



XXXVI. TeleiocHnus. 



9*. Anus without a tube 9^^. 



9''^. Arms in groups with channeled spaces between. 

 Ventral disk hemispherical. Anus excentric. 



XXXVI 1 1. Physetocrinus. 



g'\ Arms extended below in a broad rim. Ventral disk 



low. Anus subcentral XXXIX. Strotocrinus. 



3. Brachials and interbrachials but slightly represented in dorsal cup f. 



f. Monocyclic 55. 



55. Radials in contact all around. Base pentagonal ee. 



ee. Costal s two XXV. Coccocrinus. 



ee. Costal one 6f . 



6f. Column circular, with large canal XXVI. Marsipocrinus. 



6f. Column elliptic, with small canal XXVII. Platycrinus. 



55. Radials separated at posterior side by anal plate. Base hexagonal. 



ff. 



ff. Basals directly followed by the radials 7f. 



7t. Basals three XXVIII. Arthracantha. 



7t. Basals two 10*. 



10*. Costals two XXIX, Dichocrinus. 



10*. Costal one, very small, sometimes hidden \o''. 



10''^. Anal plate resembling anterior radial in form and size. 

 XXX. Talarocrinus. 

 lO''^. Anal plate much smaller than the radials. Radial 

 dome plates produced into wing- like appendages. 



XXXI. Pterotocrinus- 

 ff. Basals separated from the radials by accessory pieces. 



XXXII. Acrocrinus. 

 f. Dicyclic. Radials in contact except at the posterior side. 



LXIX. Crotalocrinus. 



II. All plates from radials up movable. Mouth and food grooves exposed {Plexi- 



bilia) 4. 



4. Arms non-pinnulate g. 



32 



