CANADIAN FCSSILS. 23 



Genus Hyboceinus, Billings. 



(Hybocrinus, Report Geological Survey of Canada, 1856, page 2Y4.) 



Formula : 

 Basal plates, 5. I Azygos inter-radials, 2. 



Radial plates, IX 5' ' Regular inter-radials, 0. 



Figure 9. 

 Figure 9. Diagram of the structure of the cup of the genus Hybocrinus. 



Generic characters. — Cup, globular or pyriform, more protuberant 

 upon one side than on the other, composed of five basal, five radial, 

 and two azygos plates. The five basal plates are pentagonal, and 

 alternating above them is a row consisting of one large azygos plate 

 and four of the radials. The large azygos plate supports upon its 

 upper right-hand sloping edge the second small azygos, and on the 

 left the fifth radial. The arms in all the species that have yet been 

 discovered are undivided, and each is composed of a single series of 

 joints. The column is round and short. The generic name is 

 derived from the Greek hubos (bent outwards or hump-backed). 



Hybocrinus peistinus, Billings. 

 Plate I. Figure '2a. 



Descriptio7i. — This little species is usually about three lines in 

 height and four lines in width, measured across the cup from the 

 posterior to the anterior side. The anterior side is very protuberant, 

 and the plates, although they appear smooth to the naked eye, yet, 

 when a little magnified, are seen to be covered with small irregular 

 tubercles. The arms are single and somewhat narrowly rounded on 

 the back, the joints about one line in length. The column is round, 

 half a line in thickness, and composed of joints which are, as far as 



Note. — In the expression radial plates, 1X5, the figure 1 indicates the number of 

 plates in each primary ray, and the figure 5 the number of rays. In the diagram the 

 shaded plates are the azygos inter-radials. 



