332 PROCEEDINGS OF THE ACADEMY OF 



should the Crinoid have so frequently left the Platyceras to grow within ita 

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

 aperture of its shell over the opening supposed to be its own 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 Criuoids, 

 believe that they ever used these appendages to hand directly to the mouth, 

 even minute organisms* 



But we believe the strongest argument against the conclusion that 

 the Criuoids, 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 Mollusk, 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 life of the latter must have 

 necessarily been of very short duration after it came in contact with the Cri- 

 noid. Yet we have the most conclusive evidence that such was not the case ; 

 but that on the contrary, in most if not all of these instances, the Platyceras 

 must have lived long enough in contact with the Crinoid to have adapted the sinuosi- 

 ties of the margins of its shell exactly to the irregularities of the surface of the 

 Crinoid. 



We have taken some trouble to examine carefully a number of specimens 

 of Plati/crinus heinisphcericus, and Goniasteroidocrinus tuherosus, from Crawfords- 

 ville, Indiana, with each a Platyceras attached, and in all cases where the 

 specimens are not too much crushed or distorted, or the hard argillaceous 

 shaly matter too firmly adherent to prevent the line of contact between the 

 shell and Crinoid to be clearly seen, the sinuosities of the lip of the former 

 closely conform to the irregular nodose surface of the latter. Owing to the 

 fact that in some cases the shell has evidently been forced by accidental 

 pressure against the surface of the Crinoid, so as to become somewhat 

 crushed, this adaptation is not always so clearly evident; but in most cases 

 it is more or less visible, while in some it is strikingly manifest. In one 

 instance of a Platycrinus now before us, with a Platyceras attached, as usual, 

 to its side, between the arm-b3ses of two of its adjacent rays, and of rather 

 larger size than those usually found attached to this species, the adaptation 

 of the irregularities of its lip, so as to receive the little nodes and other 

 prominence of the Crinoid, is so clearly manifest that a moment's examination 

 must satisfy any one that the shell must have grown there. Being, as we 

 stated, a larger individual than we usually see so situated, it not only occupies 

 the whole of the interradial or anal space to which it is attached, but its 

 lateral margins on each side coming in contact with the arm-bases of the 

 Crinoid, as the shell increased in size, had formed on either side a profound 

 sinus in its lip for the reception of these arms. These sinuses are not only in pre- 



* la many instances it is clearly evident that it would have been an absolute impnsnhility 

 for certain types of our Carboniferous Crinoids to have handed any object great or small, di- 

 rectly 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 pro- 

 boscis, to nave been flexible, and the Messrs. Austin even thought it was especially de- 

 signed and used for the purpose of sucking out the softer parts of Polyps. If flexible, we 

 might suppose that in those eases 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 exami- 

 nation always showed that, where this was not due to an accidental fracture after the ileath 

 of the animal, it was caused by the plates composing it being on one side larger, or 

 dilTerentlv lormed 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 eases out often, if not more frequently, when not aceideuially 

 distorted, found to be perf«ctly straight, or a little inclined to one side or the other. 



[Dec. 



