REPORT OF THE DIRECTOR IQIO 



219 



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

 lines and bisected by the latter. 



These ridges are covered cylindrical, epithccal extensions of 

 sutural canals and each zvas occupied by a bifurcating contractile 

 b.v. zvhose anus lay parallel to the plate surface and communicated 

 with 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 

 therefore the longest exposed 

 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 



Fig. 7 View of a portion of the holotype of P a 1 a e- 

 ocrinus striatus Billings. From a photomi- 

 crograph, xio 



covermsfs. 



