﻿schuchert] 



SILUKIC AND DEVONIC CYSTIDEA 



229 



Group of P. clarki 

 Elongate in outline. Ambulacra extending to the column. Anal 

 area composed of an apparently incomplete outer circle oi pieces and 

 an inner pyramid. 



Group of P. perdewi 

 Pear-shaped in outline. Ambulacra occupying less than two-thirds 

 of the periphery of the theca. Anal area as in the P. gordoni group. 



Of foreign species of Pseudocrinites, there are but two — P. bi fas- 

 cia tits Pearce and P. magniiicus Forbes — and these are of the P. 

 gordoni group. Forbes states that the former has 12 to 16 brachioles 

 on each ambulacrum, but this number apparently includes only those 

 of one edge, as is shown by his figure 3 of plate xi. The total num- 

 ber of brachioles in this species appears, therefore, to be from 48 to 

 04 (Jaekel gives about 80). P. bifasciatus is consequently closely 

 related to P. claypolei and P. stcllatus, but in both of the latter 

 the pectinirhombs are much more pronounced. P. magniiicus is 

 somewhat larger than P. gordoni, and has about 136 brachioles 

 (Jaekel gives 100 to 120), but differs from American species in the 

 smaller pectinirhombs and the different thecal ornamentation. Both 

 these English species occur in the Siluric near Dudley ; P. bifasciatus 

 in the Wenlock limestone, and P. magniiicus in the same horizon and 

 in the Lower Ludlow. 



PSEUDOCRINITES GORDONI Schuchert 



(Plate XXXVI, figures 8-12; Plate XXXTX, figures 11-13) 



Pseudocrinites gordoni Schuchert, Amer. Geol., 1903, xxxn, p. 235. 



Length of the largest theca 32 mm. ; greatest width 32 mm. ; depth 



21 mm. For general form, shape of individual plates and their 



ornamentation, see the figures and diagram, figure 29. 



