26 



CANADIAN FOSSILS. 



Genus Rhodocrinus, Miller. 



(Rhodocrinus, Miller, 1821. Natural History of the Crinoidem, page 106.) 

 (GiLBBRTSOCRiNUS, Phillips, 1836. Geology of Yorkshire, vol. ii., page 207.) 

 (Thtsanocrinus, Hall, 1852. Pal<Eontology of New York, vol. ii., p. 186.) 



Formula 



Basal plates, 5. 

 Sub-radial plates, 5. 

 Radial plates, 3X5. 



Regular inter-radials, 6 to 8x4. 

 Azygos inter-radials, 7 to 12. 





Figure 11. 

 Figure 11. Diagram of the structure of the cup in the genus Rhodocrinus. 



Generic characters. — Cup, globular or oval ; arms, long, often much 

 branched, and densely fringed with pinnulae ; basal plates, five, 

 alternating above which are five sub-radials ; primary rays, five, 

 consisting of three plates each ; secondary rays, ten, the number of 

 plates in each varying from one to four. The number of regular 

 inter-radials varies from six to eight, while the azygos inter-radials 

 are more numerous. The free arms spring from the secondary 

 radials. In all the Canadian species the column is round, strongly 

 annulated in the upper portion, and smooth below. The radix or 

 base of attachment consists of a number of small, branching roots. 

 The ambulacral orifices are situated at the bases of the arms, and 

 the mouth, in all the species in which it has been observed. ^*«' 

 excentric. 



