NO. 1846. 0\ CERTAIN ELEUTIIEROZOIC PEL2IAT0Z0A—KIRK. 113 



tained throughout Kfe. In the majority of cases, however, detach- 

 ment from the bottom took place. Detachment became effective 

 through the resorption of the stalk near its base. This resulted in the 

 freedom of the organism. Detachment in the case of these crinoids 

 apparently occurred at widely different periods in the development 

 of the animals, for attached forms of wadely different sizes may be 

 observed. Figure 14, Plate 11, probably represents the approximate 

 size at which detachment normally occurs, for the majority of attached 

 individuals seem to be of about this size or smaller. 



Subsequent to detachment Edriocrinus perhaps moved from place 

 to place hj crawling on its stout arms. The position assumed by the 

 specimen of E. sacculus as given on Plate 11, figure 15, is probably the 

 natural one. As here shown Edriocrinus is crawling over the surface 

 of a large gastropod. It does not seem possible with the compara- 

 tivelj'- feeble musculature of this genus and the stout arms that are 

 borne that the animal could have been capable of ver^^ effective 

 s\\amming movements. 



The origin of the peduncle as possessed by Edriocrinus may not 

 certainly be determined. It seems probable, however, that it consists 

 in part at least of fused columnals. Early in the ontogeny of the 

 animal it may well be that the crinoid became detached from its 

 embryonic stem and swam about freely with but a few columnals 

 attached to the theca. Instead of thereafter maintaining a detached 

 existence the crinoid settled doA\Ti and became cemented to some 

 object on the bottom. Subsequently a coalescence of the constituent 

 columnals took place, resulting in the formation of such structures 

 as we find. 



Edriocrinus has been placed among the Flexibiha largely from the 

 want of a better place to put it. Its apparent lack of pinnules has 

 caused it to be grouped with the Impinnata. It does not seem evident 

 that tliis grouping is correct, for the genus does not behave as one 

 would expect a member of the Flexibilia to do. The evidence of 

 the lack of pinnules is highly inconclusive. Indeed I tliink that the 

 use of this character in classification must be attended with con- 

 siderable caution. There has probably never been a crinoid which 

 might truly be styled impinnate. The pinnulse may be more in the 

 nature of tentacles perhaps and need not be strengthened by calcified 

 ossicles but they are nevertheless pinnulse. Upon occasion centers 

 of calcification may appear within these pinnules and ossicles be 

 formed. Even with the formation of definite ossicles it does not 

 necessarily foUow that the pinnules would be preserved to us to-day 

 unless there be a very close union between the constituent ossicles 

 and between the pinnulfe and the arm proper. Bather argues for 

 the origin of pinnules from bifurcation of the arm, but I hold that 

 94428°— Proc.N.M.vol.41— 11 8 



