336 PALEONTOLOGY OF ILLINOIS. 



thick, close-fitting calcareous pieces, and with even its digestive sack, 

 as we have reason to believe, at least to some extent, similarly con- 

 structed, 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 allowed it a radius of a foot or so of area to 

 seek its prey in; while the mollusk it is supposed to have so frequently 

 devoured, from its close affinities to the genus Capulm, may be sup- 

 posed to have almost certainly lived most of its life attached to one 

 spot.J In such a case, why should the Crinoid have so frequently left 

 the Platyceras to grow within its reach to nearly its adult size before 

 devouring it ? But if from some unknown cause it should have done 

 so, by what means could the Crinoid have pulled loose the Mollusk 

 (which from analogy we may reasonably suppose held with some 

 degree of tenacity to its place of attachment), and placed it with the 

 aperture of its shell over the opening supposed to be its mouth '? That 

 it could have used its arms and tentacula as prehensile organs, in this 

 sense, is extremely improbable from their very structure, so much so 

 indeed that few if any of the best authorities who have investigated 

 the recent Crinoids, believe that they ever used these apendages to hand 

 directly to the mouth, even minute organisms.* 



But we believe the strongest argument against the conclusion that 

 the Crinoids, so frequently found with the shell of a Platyceras attached 

 to them, died while in the act of sucking out, or otherwise extracting 

 the softer parts of these Mollusks, remains to be stated. In the first place, 

 if such really was the nature of the relations between the Crinoid 

 and the Mollusk, it is of course self-evident that the continuation of the 



t Mostof the best European authorities on palaeontology refer these shells even to the existing genus 

 Capulus, 



* In many instances it is clearly evident thai il would have been an O&solute inij>ii>is!l/ilit// for certain 

 types of our Carboniferous Crinoids to have handed any object, great or small, directly, to the only 

 opening through the vault. That is, where this opening is at the extremity of a straight rigid tube. 

 often nearly twice the length of the arms, even to the extreme ends of their ultimate divisions. We 

 are aware that some have supposed this tube, or proboscis, to have been flexible, and the Messrs. 

 AUSTIN even thought it was especially designed and used for the purpose of sucking out the softer 

 parts of Polyps. If flexible, we might suppose that in those cases where it was so much longer than 

 the arms, that it could have been curved so as to bring its extremity within reach of the ends of the 

 arms ; but although we, have in a few instances seen this tube more or less bent, a careful examination 

 always showed that, where this was not due to an accidental fracture after the death of the animal, it 

 was caused by the plates composing it being on one side larger, or differently formed from those on the 

 other, and evidently not to flexibility. We find the arms, which were evidently flexible, folded and 

 bent in every conceivable manner, but the tube of the vault is, in nine cases out of ten, if not more 

 frequently, when not accidentally distorted, found to be perfectly straight, or a little inclined to one 

 side or the other. 



