CANADIAN FOSSILS. 21 



In the "Natural History of the Crinoideae" Miller described this 

 genus as having only three basal plates, an error into which it was 

 easy for him to fall, on account of the minuteness of these plates in 

 most of the species. In consequence of this mistake, several other 

 genera were founded on specimens with five basal plates ; but as it 

 has been ascertained that Miller's original specimens have also five, 

 these genera cannot be retained. 



In the Report of the Geological Survey of Canada I referred with 

 doubt two of our species, R. pyriformis and R. microbasalis, to the 

 genus Thysanocrinus of Hall. They are very clearly congeneric 

 with the Thysanocrinus liUformis of the Niagara limestone, while 

 they have also in general the same structure as Rhodocrinus. There 

 are however some differences in the form of the body and the upper 

 parts which led me to think the genera might be distinct ; but not 

 being decided, I referred them to Thysanocrinus, at the same time 

 giving the other name in a parenthesis. During the last summer I 

 discovered the small species, R. asperatus, which has not only the 

 structure but the aspect also of the typical forms of Rhodocrinus^ 

 and I think therefore that our three species should be placed in that 

 genus. 



Rhodocrinus asperatus, Billings. 



Plate I. Figures 4a-4e. 



Description. — Cup, small, nearly globular; surface covered with 

 numerous small, conical, irregular tubercles. The basal plates are 

 so exceedingly diminutive as to be entirely concealed within the 

 cavity in the centre of the base in which the column is inserted. 

 The column is round, and strongly and closely annulated near the 

 base with very thin, sharp, projecting joints or rings, as in the other 

 species of this genus. Judging from some fragments found associated 

 with the specimen figured, it would appear that the arms are long 

 and thickly fringed with well-developed pinnulae. Height of cup in 

 the only specimen discovered, six lines ; diameter, the same. 



Explanation of Figuees. Plate I. 



Figure 4a. Side view of the specimen. 

 " 4&. View of the base. 



" 4c. A radix found in the same slab along with Aa. 

 " 4rf. Portion of the surface of 4c magnified. The joints of this column 



appear to be composed near the root of five pieces each, which 



interlock, as represented in the figure 4d. ' 

 " 4e. Transverse section of the column near the root. 



