﻿SMITHSONIAN MISCELLANEOUS COLLECTIONS 



[vol. 47 



or incomplete circle of from 6 to 8 pieces and the pyramid of J pieces. 

 One basal and 2 upper pectinirhombs normally situated, with long, 

 angulated, grooved, adjoining recesses, and numerous dichopores. 



Ambulacra 2 in number, apparently R I and R IV (see remarks on 

 Trimcrocystis). These extend along the narrow periphery of the 

 theca and in most species touch the column. Brachioles abundant. 

 The piece with the madreporite and a depression diagonally opposite 

 separates the 2 ambulacra. 



Column stout near the theca, tapering more or less rapidly, and 

 composed of equal-sized pieces with angulated margins. Beneath 

 this upper section the column maintains a nearly equal diameter, and 

 the pieces may be interspersed with larger ones, all having a rounded 

 periphery. 



Genotype, P. bifasciatus Pearce. The above diagnosis, however, 

 is based on P. gordoni. Of the former there is a specimen in U. S. 

 X. M. ; cat. number 35,138. 



Pseudocrinites is readily distinguished from the other Siluric 

 genera of cystids by the fact that it has but 2 ambulacra, sometimes 

 called recumbent arms. In all other associated genera there are 3 or 

 4 of these arms. 



The number and arrangement of the thecal plates are the same in 

 all species (except P. abnormalis). The specific characters are form, 

 arrangement of anal plates, length of ambulacra, number and length 

 of brachioles, nature of ambulacralia, and number of dichopores. 

 On the basis of these characters, eight new species are here described. 

 To facilitate easy reference, these forms and their specific features are 

 tabulated as follows : 



Table of Characters of American Species of Pseudocrinites. (Based on 

 Average-sized or Fully Adult Specimens) 



Group of P. gordoni 



Circular in outline. Ambulacra extending to the column. Anal 

 area composed of 1 outer complete circle of pieces and an inner 

 pyramid. 



