NATURAL SCIENCES OF PHILADELPHIA. 331 



liisk was directed upward, wbeu the vault of the Crinoid was turned in that 

 direction.* A species of Goniasleroidocrinus [O. tuberosus, Lyon and Casse- 

 day), found at the same locality, also has frequently a Plali/ceras attached to 

 the top of its nearly flat vault, so as to cover the only opening in the same. 

 It is wortiiy of note, however, that it is always another, subspiral, Flatyceras 

 (very similar to P. nequilaterum), that we find attached to this Crinoid, so that 

 here at least, it would seem that each of these two Crinoids has its own par- 

 ticular species of Plafyceras. 



In all of these, and numerous other examples that might be mentioned, it is 

 worthy of note that it is to species of Crinoids Avith 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 ;-j- and it is so rarely that we find shells of any other 

 genus than Plati/ceras, appareuth^ attached to, or in contact with, the body of 

 a Crinoid, that it seems probable wliere other shells are occasionally so found, 

 that their connection with the Crinoid may lie merely accidental. If it coulil 

 be established as a fact, that these Crinoids were actually devouring these 

 Mollusks, by sucking out, or otherwise extracting and swallowing their softer 

 parts, in any instance where they have been found with a shell attached over 

 the opening of the vault, this would, of course, establish the fact that this 

 opening is the mouth, or, at least, that it must have performed the office of 

 both oral and anal aperture. But to say nothing in regard to all that is known 

 of the habits and food of the recent Crinoids beingso directly opposed to such 

 a conclusion, the fact that so large a proportion as nearly one-half of all the 

 individuals of some species should have died at the precise moment of time 

 when they were devouring a Plafyceras, and should have been embedded 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 principal 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 liave 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 nearlj- 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 allowed it a radius of a foot or so of area to 

 seek its prey in ; while the mollusk it is suppose 1 to have so frequently de- 

 voured, from its close affinities to the genus CapuLus, may be supposed to have 

 almost certainly lived most of its life attached to one spot. J In such a case, why 



* Prof. Ricliard Owen has noticed, in his Report on the Geological Survey of Indiana, p. 

 364 (18(52), the frequent oeeurrenee of a Plattjcras attached to this same Platycrinus, at this 

 locality, and propo.sed to name the PUdyccrns P. pabiilncriniis, from the supposition that it 

 formed the chief food of these Crinoids. It is probable that the Pliti/ceras for whioh he 

 proposed this name, is the same we named P. in/umUbiUum, but as he gave no description 

 of the species, and but an imperfect figure, we oanuot spei\k p'lsilinlt/ as to its identity. 

 Prof. Hall has also proposed the name of /^. subrectum for this Crawfordsville /"<rti/':'ra.i, liu t 

 he had previously used the same name for a very different, Kew York, Devonian species 

 of this genus. 



Prof. Yandell and Dr. Shumai'd have also figured in their paper entitled "Contributions to 

 the Geology of Kentucky," a specimen of Acrucrinus, with a very simdar Platyceras appar- 

 ently attached to its vault. 



Amongst all the numerous Crinoids found at Burlington, Iowa, we are aware of but a 

 single instaneeof one being found withaPta^ycerajjattached, and that is a specimen nf Acti- 

 nocrinus venlricosus in Mr. Wachsmuth's collection, which has a crushed shell of a I'lalyci-ras 

 connected with its vault. 



t Possibly due to the fact^ that in species with a proboscis there is much less room for 

 attachment to the vault. 



i Mo.st of the best European authorities on palaeontology refer these shells even to the 

 existmg genus Cajjidus, 



1868.] 



