FOSSILS OF THE nrilLINclTOX GROUP. 335 



the vault of the Crinold was turned in that direction.* A species 

 of Goiiinxttroirtocrinm (G. iuberoxus, Lyon and Casseday), found at 

 the same locality, also has frequently a Platycera* attached to the 

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

 same. It is worthy of note, however, that it is always another, 

 subspiral, Platyceras (very similar to P. cequilaterum), that we find 

 attached to this Crinoid, so that here at least, it would 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 men- 

 tioned, 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 probos- 

 cis, that we find these shells attached in this way,t and it is so rarely 

 that we find shells of any other genus than Platyceras, apparently 

 attached to, or in contact with, the body of a Criuoid, that it seems pro- 

 bable where other shells are occasionally so found, that their con- 

 nection with the Criuoid may be merely accidental. If it could 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 aperature. But to say no- 

 thing in regard to all that is known of the habits and food of the recent 

 Crinoids being so 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 Platyceras, and should have been imbedded in the sedi- 

 ment 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 principle an 

 animal with its viscera incased in a hard unyielding shell, composed of 



* Prof. RICHARD OWES has noticed, in his Report on the Geological Survey of Indiana, p. 364 (1862), 

 the frequent occurrence of a Platycera* attached to this same Platycrinus, at this locality, and pro- 

 posed to name the Platyceras P.pabulocrinus. from the supposition that it formed the chief food of 

 these Crinoids. It is probable that the Platycera* for which he proposed this name, is the same we 

 named P. infnndibulum. hut as he gave no description of the species, and bnt an imperfect figure, we 

 cannot speak positively as to its identity. Prof. HALL has also proposed the name P. subrectum for this 

 Crawfordsville Platycera*, bnt he had previously used the same name for a very different. Xew York, 

 Devonian species of this genus. 



Prof. Y.vM'F.i.L and Dr. SHCMARD have also figured, in their paper entitled "Contributions to the 

 tjf,,]f>'jr\- of Kentucky," a specimen of Acrocrinvf. with a very similar Platyceras apparently attached 

 t<> iti* vault. 



Amongst all the numerous Crinoids found at Burlington, Iowa, we are aware of bnt a single instance 

 of one being found with a Platyctra* attached, and that is a specimen of Actinocrinvx rentricoztis in 

 Mr. WACH^MITH'S collection, which has a crushed shell of a Platyceras 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. 



