﻿REPORT OF THE DIRECTOR I9IO 



219 



lengths, parallel to each other, nearly perpendicular to the sutural 

 lines and bisected by the latter. 



These ridges are covered cylindrical, epithecal extensions of 

 sutural canals and each was occupied by a bifurcating contractile 

 b.v. whose arms lay parallel to the plate surface and communicated 

 zvith the interior only through the sutural canal itself. 



In support of the above assertion we may first examine figure I 

 of plate 5, which presents a detail of the left posterior margin — a 

 portion of the best preserved belt of the specimen. Erosion, though 

 slight, has carried away just enough of the crests of some of the 

 horizontal ridges to reveal in part their hollow nature and at a an 

 ascending ridge has been so broken across that a portion of its cavity 

 is clearly brought to view. 

 Text figure 7 represents a por- 

 tion of the right posterior 

 margin, a detail from the op- 

 posite edge of the best pre- 

 served belt. The ascending 

 ridges have had their crests 

 removed to a still greater ex- 

 tent and the broken edges at ' 

 times reach deep enough to re- 

 veal nearly the full width of 

 the canal itself. 



That these structures were 

 epithecal, that is laid down 

 over the mesostereom, and 

 that they have no communica- 

 tion with the interior through 

 the plate itself, is shown by 

 text figure 8, which represents 

 that portion of the specimen 

 which we have already consid- 

 ered as lying uppermost in the 



bedding plane and which WaS Fig. 7 View of a portion of the holotype 

 r ocrinus striatus Billings. From 



therefore the longest exposed crograph, xio 



to the effects of weathering. The r.ant.B. has lost nearly all traces 



of its canals, but the floors of these structures may be seen on the 



margins of the adjacent plates to the left and we have to pass but 



little distance over the edge of r.ant.IB to reach the less weathered 



belt and find at a and b first the side walls and then the canal 



coverings. 



of P a 1 a e- 

 a photomi- 



