i 
1888, ] 23 9 [Keyese 
the arms of Glyptocrinus decadactylus Hall. This writer in his descrip 
tion* of Acrocrinus.shumardi also calls attention to a Capulus on the vault 
of that species as clearly proving the carnivorous habits of the crinoid- 
eans: Jelocrinus globosus Dewalque, with a Platyceras adhering, has 
been found in the schistes de Frasnes & Senzeille by Fraipont,+ who says : 
‘*Cette position du mollusque sur de crinoide vient apporter une preuve 
de plus contre l’opinion des paléontologues qui soutiennent que les Capu- 
lus rencontrés sur ces crinoides servaient de nourriture & ceux-ce.’’ 
Finally, Meek and Worthen} mention a Platyceras adhering to the side of 
a Pentremites godont ‘so as to cover one of the pseudo-ambulacral fields 
and two intermediate areas ”’ 
Ill. Summary. 
When attention was first directed to fossil crinoids having Platycerata 
attached, conclusive proof of their carnivorous habits was thought to 
be established, and inasmuch as it was then considered that the aper- 
ture in the vault was the mouth, this explanation for a long time ap- 
peared very plausible. Consequently the conclusion was very naturally 
reached, that the crinoid when it perished was in the act of devouring the: 
mollusk. Meek and Worthen§ seem to have been the first to demonstrate 
that the prevalent opinions regarding the intimate association of crinoid 
and Platyceras were erroneous, and that the gasteropod was undoubtedly 
stationed on the crinoid for a protracted period, and very probably even’ 
for the greater portion of its life. But notwithstanding the fact that the 
univalve was almost invariably situated over the ventral aperture, and 
that this opening was recognized as the anus, these writers do not appear 
to have entertained for a moment the idea that the gasteropod may have 
been nourished on the refuse matter from the crinoid. The latter view 
was more recently advanced by Wachsmuth, and has since been favorably 
received by other paleontologists. In all of the specimens lately exam- 
ined—probably upwards of one hundred and fifty—the Platyceras covers 
the anal opening of the crinoid, and as far as observable, it is always the 
anterior portion of the molluscan shell that is directed towards the vault 
aperture. In those examples in which the shell has been removed, its 
impression made on the ventral surface shows that the anterior margin of 
the peristome was at the edge of the opening in the dome—a position that 
would have brought the mouth of the mollusk directly over the anal aper- 
ture of the crinoid. The food of recent crinoids consists chiefly of ani- 
malcules and microscopic plants, and the living Calyptreide subsist on 
food of a similar nature, From analogy it might be inferred that the food 
of the fossil crinoids and mollusks must have been like that of their recent 
representatives. So far as these echinoderms are concerned, there appears 
* Am. Jour. Sci., (2), Vol. xx, p. 135. 
+ Annal Soc. géol. de Belgique, t. x, Mémoires, 1883, ‘p. 62. 
t Geol. T1l., Vol. iii, p. 386. 
§ Proc. Acad. Nat. Sci. Phila., 1868, p. 340, et seq. 
PROC. AMER, PHILOS. SOC. XXV. 128. 2H, PRINTED DEC. 21, 1888. 
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