36 CANADIAN FOSSILS. 



This genus is exactly the same in the composition of the test as 

 Cyathocrinus with the exception of the peculiarity that one of the 

 rays has two of its joints contained in the walls of the cup. In the 

 original description given by Professor Hall, (Pal. N. Y., vol. 2, 

 p. 193,) four series of plates are mentioned, including five " scarcely 

 visible " plates beneath those which I regard as constituting the true 

 base ; they cannot be seen in any of the specimens in the collection 

 of the Survey, although at least four of the species are unquestionable 

 congeneric with D. longidactylus (Hall). 



I have seen Professor Hall's specimens, and he agrees with me 

 that the generic description may be so modified as to receive many 

 species with the same structure in other respects, but which do not 

 exhibit the small plates at the base. It will be seen by referring to 

 fig. 7, c, plate 42, vol. 2 Pal. of New York, that the column of D, 

 longidactylus consists of alternately large and small (or thin) joints, 

 and that the latter sometimes consist of five divisions. Professor 

 Hall is now of opinion that the small pieces at first regarded as 

 constituting the true base are not of generic importance, and that 

 they may be considered either as one of the quinquepartate thin 

 plates of the column, or as a basal series so little developed as not to 

 be of more than specific value. 



It will be recollected by those who have studied the Crinoideae, 

 that a similar question relating to the base of Poteriocrinus still 

 remains unsettled ; Professor Philips and the Messrs. Austin having 

 published that genus with three minute plates situated under the 

 three basal plates. 



Dendrocrinus gregarius, Billings. 

 Plate ni. Figures la, lb, Ic. 



(D. GEEQAEius, Report Geological Survey of Canada, 1856, page 265.) 



Description. — Cup, acutely conical, from three to eight lines in 

 length, and from two to six lines broad at the greatest diameter, 

 which is at the margin, whence to the small pointed base it tapers 

 uniformly with nearly straight sides ; basal plates, narrow, nearly 

 one third the height of the cup ; sub-radials, rather more than one 

 third broader than high ; large azygos inter-radial, not quite so large 

 as the plate on which it stands, broader above than below ; proboscis, 



