1 38 ECHINODERMATA PELMATOZOA SUB-KINGDOM in 



dislirhdl* n<l inki-pnlmurs often, and in most cases anals also present. Arms 

 uniserial or Userial, and pinnulate. Ordovician to Carboniferous. 



[Analysis of Families, according to Wachsmuth and Springer. 1 



I. 



Lower brachials and interbrachials forming an important part of the dorsal 

 cup. 



A. INTERRADIALS ILL-DEFINED. 



The lower plates of the rays more or less completely separated from those of other 

 rays, and from the primary interradials, by irregular supplementary pieces. Anal 

 interradius divided by a row of conspicuous plates. Dicyclic or monocyclic. 

 RETEOCRINIDAE. 



B. INTERRADIALS WELL-DEFINED. 



1. Dicyclic 



(a) Radials in contact except at the posterior side. THYSANOCRINIDAE. 



(b) liadiah separated all around. RHOPOCRIXIPAE. 



2. Monocyclic 



(n) Jtit'fiitlfi iii contact all around. 



Symmetry of the dorsal cup, if not strictly peutamerous, disturbed by the introduction 



of anals between the brachials only. MELOCRINIDAE. 

 Arms borne in compartments formed by partitions attached to the tegmen. Dorsal cup 



perfectly pentamerous. Calyx plates limited to a definite number. CALYPTOCRINIDAE. 



(b) Radials in contact except at tlie posterior side, where they are separated by an anal plate. 

 First anal plate heptagonal, followed by a second between two interbrachials. BATO- 



CRINIDAE. 



First anal plate hexagonal, followed by two interbrachials without a second anal. Arms 

 branching from two main trunks by alternate bifurcation. ACTINOCRINIDAE. 



II. 



Brachials and interbrachials but slightly represented in the dorsal cup. 



1. Dicyclic 



Radials in contact except at the posterior side. CROTALOCRINIDAE. 



2. Monocyclic 



(a) Radials in contact all around. Base pentagonal. PLATYCRIXIDAE. 



(b) Radials separated at the posterior side by an anal plate. Base hexagon*/. 



Basals followed directly by the radials. HEXACRINIDAE. 



Basals separated from radials by accessory pieces. AcROCRINIDAE.] 



Family 1. Platycrinidae. Roemer. 



Dorsal cup composed of a monocyclic base and a circlet of five large radials, 

 without special anal plate. The lower brachials, which form part of the calyx, similar 

 in form and size to tlie free arm- joints. Interradials heavy, restricted almost 

 exclusively to the tegmen ; only those of the first row to a certain extent interbrachial. 

 Arms often numerous, generally free from the distichals upwards; uniserial or 

 Userial. Pinnules well developed. Silurian to Carboniferous. 



1 [ Wachsmuth, C., and Springer, F. The Crinoidea Camerata of North America (Memoirs 

 Museum Comp. Zool. vol. xxiv.) In press. The above is extracted from proof-sheets kindly 

 furnished by the authors. TllANS.] 



