﻿chuchert] siluric \xn devonic cystidea 255 



"The basal portion occupies a subcircular area, which is placed 

 in a central position with regard to the disposition of the lobes of the 

 body, and is surrounded by an elevated projection or extension of the 

 walls, [n structure this area is composed of spreading, radici- 

 form, bifurcating rays, connected by irregular polygonal plates. I h< 

 basal ra\s are composed of joints similar to those of an ordinary cri- 

 noidal column, and vary in number from five to twelve or more, and 

 are arranged symmetrically with respect to two axes at right angles; 

 they bifurcate at the third or fourth segment from their origin, and 

 enclose ambulacra! openings which penetrate into the interior cavities 

 ( if the b< »dy. 



" The external wall of the dome is composed of two distinct layers, 

 of which the infolding and extension of the inner one forms the 

 partitions dividing the chambers. No traces of free arms have been 

 observed. Column cylindrical, smooth near the body; the segments 

 regular. The interior canal is five lobed, and is divided and con- 

 tinned through the basal rays and their ramifications; not opening 

 into any interior cavity of the body, so far as observed." 



Hall's remarks on this fossil are as follows: 



" This remarkable crinoidal body is so totally unlike any previously 

 described form, within my knowledge, that its true characters and 

 relations are not at once evident. There is no doubt as to its crinoidal 

 nature, but there is no apparent analogy of its parts with ordinary 

 crinoids. Some of its characters would indicate that it is a curiously 

 modified and enlarged summit or dome; that the visceral cavity is a 

 small internal chamber immediately over the column-attachment; and 

 that the lobes are an abnormal development of the interbrachial or 

 interradial spaces. But the more probable theory in regard to this 

 fossil, points to a functional similarity with a crinoidal root, as in 

 Ancyrocrinus from the Upper Helderberg and Hamilton groups, in 

 which there is a bulbous growth at one extremity of the column. 

 supposed to act as a float or anchor to the body and arms. Viewing 

 it in this respect, it may he regarded as a large chambered hull), with 

 an attached column, on the distal extremity of which was a calyx, 

 having characters unknown at the present time. Tn this aspect, it 

 must have been a free floating organism, similar in its habits to the 

 recent Medusa and Comatulce. The lack of definition and symmetry 

 which these crinoidal bodies assume would be an argument in support 

 of this view, and find explanation in their consequent secondary func- 

 tional importance, and separation from the governing center or 

 centers." 



