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considering them all as one. Uintacrinus, like Marsupites and 
Saccocoma, is universally conceded to have been pelagic; but so 
far, authors have not had the courage of their convictions, and, 
though saying that they are pelagic, persist in representing them 
in a very unpelagic attitude; all pelagic animals with a central 
body and streaming tentacles and arms known today float with the 
body upward, and the tentacles or arms dependent; this includes, 
in the recent seas, the numerous ctenophores and the medusæ, 
and a few cephalopods (Argonauta, etc.) all of which, like the 
similarly built octopus, maintain a position with the mouth and 
tentacles downward except sometimes when in motion, at which 
time the axis of the animal may become more or less horizontal. 
There is no reason to suppose that Uintacrinus, Marsupites, and 
Saccocoma, built on the same general plan as the jelly-fish and 
paper-nautilus (though of course widely different in detailed struc- 
ture) did not have the same position when floating free in life; 
moreover, in the case of Uintacrinus (and in the other two genera 
as well) the arms are massive and heavy, as they are in the recent 
bottom inhabiting comatulids, while the body is covered with very 
thin plates; this gives the arms a much greater relative specific 
gravity, and would insure a position in which the mouth would be 
pointing downward, and the arms dependent, the comparatively 
large thin walled body acting as a float. 
Uintacrinus probably floated about the cretaceous seas in 
more or less closely compacted masses, just as do so many of the 
ctenophores and medusæ of today; and there is no reason to 
suppose they could not have lived with their arms more or less 
interlaced and their bodies close together, as do many of the recent 
jelly-fish; it has been suggested that in such a close swarm suffo- 
eation would result; but there would be no more danger than with 
the recent medusæ, which thrive under those conditions. Moreover, 
the closer the individuals lived, the more advantageous it would 
be for them; for their food probably consisted of minute pelagic 
organisms which they intercepted with their long and feathery arms; 
