34 Meek and Worthen on Paleozoic Crinoidea. 
Diatomacecee, minute Entomostraca, etc.,* cee were conveyed 
to the mouth along the ambulacral canals, aps by means 
of cilia, we are led from satay to think that. paleozoic Crin- 
oids subsisted upon similar food, conveyed in the same way to 
the entrance of the digestive s sack, so, where would there 
have been any absolute necessity for a mouth or rather opening 
directly through the vault, when, as we know, the ambulacral 
canals were so highly developed under it from the arm openings 
to the entrance into the top of the alimentary canal? Indeed 
it seems at least probable, that if the soft ventral disc of Coma- 
tula had possessed the power of secreting solid vault pieces, as 
in most types of paleozoic Crinoids, that these vault pieces 
would not only have covered over the ambulacral furrows, as 
in the paleozoic types, but that they would also have hermeti- 
cally covered over the mouth, and converted the little flexible 
anal tube into a solid calcareous pipe, such as that we often 
call the proboscis in the extinct Crinoids. 
From all the facts therefore now known on this point, we are 
led to make the inquiry whether or not, in all the paleozoic 
Crinoids in which there is but a single opening in the vault— 
whether it is a simple aperture or prolonged into a proboscis, 
and placed posterally, subcentrally, or at some point on a line 
between the middle and the posterior side—this opening was 
not, instead of being the mouth, or both mouth and anus as 
supposed by some, really the anal aperture alone ; and whether 
in these types the mouth was not generally, if no ot always, her- 
metically closed by immoveable vault big so far as regards 
any direct opening through the vault? 
e are aware of the fact, that at least one apparently ede 
sien may be urged against this suggestion, and in fav of 
the conclusion that the single opening seen in these older Orin- 
oids was the mouth, or at least performed the double office of 
both anal and oral aperture. That is, the frequent occurrence 
of es of these ae species, with the shell of a 
to the m 
” Darin a and Hupé also state (Hist. Nat. de Zoophytes Reied, p. 18), that the 
ed Comatula was “nourished by microscopic Alge oating ue 
whis the vibratile cilia of the ambulacra s brought to the mouth.” That they may 
however, 1s not improbable, and would not, if such was the _ by any means 
disprove the generally accepted opinion that these animals received their food al- 
most entirely through the agency of their ambulacral canals. 
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