NO. 1846. ON CERTAIN ELEUTHEROZOW PELMATOZOA—KIRE: 4S 



those types in which detachment is predicated on the evidence of 

 analogous structures, or for other cause, will be discussed. As more 

 perfect material is secured, it is probable that this list of determiaable 

 free stalked crinoids will be appreciably augmented. 



Mariacrinus. — A number of observers have noted that the columns 

 of Mariacrinus are frequently found coiled in their distal portion. 

 No complete stems have liitherto been recorded, however, so it has 

 been impossible to determine the significance of this fact. Several 

 specimens of Mariacrinus paucidactylus have recently come to light, 

 the columns of wliich are essentially complete. From the evidence 

 afforded by tliis material certain interesting conclusions may be 

 drawn relative to the habits of this species, and by inference, of 

 the genus. 



In these specimens, which represent fairly mature individuals, the 

 stem is remarkably short. It tapers evenly but with moderate 

 rapidity distad and in its extreme, distal portion becomes com- 

 paratively tenuous. In each individual observed, there is a loop in 

 the distal portion of the column that forms at least one complete 

 revolution. There are no radicular cirri present, nor is there any 

 evidence that such appendages ever existed. Furthermore, there are 

 no signs of cementation by a terminal plate, though to be sure, tliis 

 may have been broken off. The columns as preserved indicate a fair 

 degree of flexibility other than is shown by the looping noted above. 



There can be little doubt but that tliis species led a detached 

 existence for the greater part of its life. The lack of structures 

 adapted to function as organs of attachment, and the distal coiling 

 of the column point strongly to this conclusion. Even were fixation 

 had by means of a terminal plate present in Hfe, and not preserved 

 to us at the present time, we could scarcely account for the looping 

 of the column. This is not a feature such as is shown by statozoic 

 types. It is probable that Mariacrinus paucidactylus was able to 

 move from place to place by means of swimming motions of its arms. 

 Wlien the animal wished to attach itself it could readily do so by 

 looping the distal portion of its stem about some object on the sea 

 bottom, or perhaps about the column of another individual. The bot- 

 tom of the Helderbergian sea was in places literally covered with 

 prostrate crinoid columns and these at times may well have served 

 as points of anchorage. 



Looping of the column seems to have been present in other species 

 of Mariacrinus, and we may be fairly safe in assuming that a detached 

 existence was largely maintained in this genus. A notable instance 

 is that of the type specimen of Mariacrinus warreni, wliich exliibits 

 a marked coihng of the distal portion of the stem. The presence of 

 this character in species ranging from the Niagaran to the Helder- 

 bergian strongly suggests that we are deaUng with a persistent and 



