36 Meek and Worthen on Paleozoic Crinoidea. 
seem that each of these two Crinoids has its own particular 
species of Platyceras. 
In all of these, and numerous other examples that might be 
mentioned, it is worthy of note that it is to species of Crinoids 
with a simple opening in the vault, and not to any of those 
with a produced proboscis, that we find these shells attached 
in this way ;* and it is so rarely that we find shells of any 
other genus than Platyceras, apparently attached to, or in con- 
tact with, the body of a Crinoid, that it seems probable where 
other shells are occasionally so found, that their connection with 
the Crinoid may be merely accidental. If it could be estab- 
oids being so directly opposed to such a conclusion, the fact 
that so large a proportion as nearly one-half of all the individ- 
uals of some species should have died at the precise moment 
of time when they were devouring a Platyceras, and should 
have been imbedded in the sediment and subsequently fossilized 
without separating from the shell, seems, to say the least of it, 
very improbable. 
And it is even more difficult to understand upon what prin- 
ciple an animal with its viscera incased in a hard unyielding 
shell, composed of thick, close-fitting calcareous pieces, and 
with even its digestive sack, as we have reason to believe, at 
least to some extent, similarly constructed, could have exerted 
such powers of suction as to be able to draw out and swallow, 
through an aperture in its own shell, often less than one-tenth 
of an inch in diameter, the softer parts of a mollusk nearly or 
quite equal in volume to the whole of its own visceral cavity. 
That they ever did so, however, becomes still more improbable, 
when we bear in mind the fact, that the animal supposed to 
have performed this feat, lived, at least during the whole of its 
adult life, attached to one spot by a flexible stem, that only al- 
lowed it a radius of a foot or so of area to seek its prey in ; while 
* Possibly due to the fact, that im species with a proboscis there is much less 
room for attachment © val ; 
ul 
+ Most of the best a authorities on paleontology refer these shells. 
even to the existing genus Capulus. 
fe. 
oe pila 
