446 PELMATOZOA. 



Families — Haplocrinidae, Symbathocrinidae, Cupressocrinidse, Gastero- 

 comidae. 



Sub-order II. Fistulata. — Interradial and anal plates generally 

 well developed. Base usually dicyclic, and arms often biserial. Oral 

 plates generally reduced, and the calyx covered by a plated perisome 

 which often bears open ambulacra. The posterior interradius may be 

 greatly developed to form the ventral sac or anal proboscis. 



Families — Hybocrinidae, Heterocrinidae, Anomalocrinidae, Belemno- 

 crinidae, Cyathocrinidae, Poteriocrinidae, Encrinidae, Astylocrinidae, 

 Catillocrinidae, Calceocrinidae. 



Order III. Articulata. 



Crinoids in which the higher radials are more or less movably articu- 

 lated on one another, though often united laterally by the plated perisome 

 of the disc. The ambulacra are generally open and the mouth exposed, 

 though often surrounded by oral plates. Interradial and anal plates 

 rarely present : arms uniserial. 



Sub-order I. Impinnata. 

 Family — Ichthyocrinidae. 



Sub-order II. Pinnata. 



Families — Pentacrinidae, Comatulidae, Apiocrinidae, Bourgueticrinidae, 

 Eugeniacrinidas, Holopidae, Marsupitidas, Plicatocrinidae, Hyo- 

 crinidas, Saccocomidae. 



