THE CRAWFORDSVILLE CRINOIDS. 561 



ruple rows. Some of these much resemble the scales of a chicken's foot, others 

 the braids of a whip lash, others still the rows of kernels upon an ear of corn. 

 These arms contain ambulacral processes which connect with the organs of 

 nutrition within the cavity or calyx. The inner edges of these arms are fringed 

 ■with pinulae or filaments resembling the margins of a feather or quill, or with 

 tentacles. Through these delicate organs it is now supposed that the animal 

 absorbed a glutinous substance found at the bottom of the sea, which, passing 

 through the hollow spaces within the arms into the organs of nutrition within the 

 calyx, nourished the animal. This of course is at variance with the idea ad- 

 vanced in both extracts above, and illustrated by a cut in Murchison's Silurian 

 and in some early geologies, which represents a crinoid with its long, slender 

 proboscis thrust into the shell of a moUusk upon which it was supposed to be 

 feeding. But without doubt, this picture, thus explained, reverses the order of 

 nature. The mollusk was feeding upon the crinoid. Various facts confirm us 

 in this opinion. 



In the first place it is now quite well established that the proboscis, once 

 regarded as a passage for food, is really an anal tube, and that there is in the 

 Paleozoic crinoids no oral opening through the wall of the calyx except the pas- 

 sages connected with the ambulacral processes of the arms. Furthermore, we 

 have in our possession a number of specimens with moUusks, especially Platy- 

 ceras infundibulum (M. & W.) firmly attached to the crinoids, and in every "case 

 the aperture of the mollusk covers the anal opening. In all these cases there- 

 fore, the crinoid could not have been feeding upon the mollusk, unless this open- 

 ing is both anal and oral, as some suppose. If this be the case, and the crinoid 

 is really devouring the mollusk, then we should expect to find the crinoid in a 

 healthy condition in every case, and the mollusk the reverse. Now the fact is 

 that of a large number of specimens of this kind, in every instance the mollusk 

 is in a perfect and healthy condition, while the crinoids, in nearly every instance, 

 are more or less imperfect and decayed. The apparent exceptions are cases in 

 which it is evident that the mollusk became attached to the crinoid only a short 

 time before both perished. It is exceedingly interesting to note the different 

 stages of decay in the crinoid as illustrated in the specimens alluded to. First 

 there is a slight depression of the calyx opposite the anal ; then it is cupped more 

 and more. Finally the calyx is completely collapsed, and so the process con- 

 tinues until nothing is left but the plates and rings, which lie scattered about the 

 aperture of the mollusk, which has continued to become more stout and robust 

 throughout the entire process. I have repeatedly found a Platyceras equilatera 

 attached to the anal tube of Actinocrinus indianencis , and A. tamulosus, and inclosed 

 within the arms. At first I congratulated myself upon the discovery of a case 

 in which the crinoid was actually feeding upon the mollusk. Examining the 

 specimen more carefully, I discovered that the proboscis was entirely gone, and 

 the plates were lying about the aperture of the mollusk, and that the aperture 

 was fastened upon the vault and directly over the opening into the cavity. A 

 ^r<eat number of such specimens as these have convinced the writer that vast 



