REPORT ON THE CRINOIDEA. 87 



the greater part of the interior of the cup, but not reaching down to the basals, is a 

 laro-e convoluted organ, which lias a general resemblance to the shell of a Bulla. It is 

 open at both ends, and its longer axis nearly coincides with that of the body of the 

 Crinoid. Wachsmuth and Springer' describe its wall as being " simple in all cases, very 

 delicate, and constructed of an extremely fine filigree work, which generally in the fossil 

 became thickly incrusted with siliceous matter on both sides." Hall, who was the first to 

 notice this orwan, made no suggestions respecting its nature. Meek and Worthen supposed 

 it to be a kind of framework supporting the coiled digestive tube ;^ while Wachsmuth and 

 Sprino-er suo-gest that it might be " an extensive plexus of blood-vessels surx'oundiug the 

 ambulacral (1) canal ; " and desiring that it " should receive a more appropriate name 

 than any yet given," they propose to call it the " oesophageal network."' 



That it supported some of the intervisceral blood-vessels I have very little doubt; 

 but there is no reason to suppose that it actually represents the vessels themselves, which 

 would have passed through the meshes of its network (compare PI. LVII. fig. 5). As 

 a similar though less developed structure occurs in recent Crinoids, I see no reason to 

 douljt the correctness of Meek and Worthen's determination. 



Neither do I think Wachsmuth and Springer's name a good one, for it implies that 

 the structure in question was connected with the oesophagus, and not with the rest of the 

 digestive tube. But as it is so large, relatively to the interior of the calyx, the remainder 

 of the digestive apparatus must in that case have been quite small, which is improbable 

 for many reasons. 



According to Meek and Worthen,* " its slightly dilated upper end seems to stand 

 with its middle almost, but apparently not exactly, under the middle of the nearly 

 central proboscis of the vault ; while at the anterior side of its upper margin, and a httle 

 out from under the proboscis, it shows remains of a kind of thickened coUar, which we 

 found to l^e composed of minute calcareous pieces. From this there radiate five 

 ambulacra, composed of the same kind of minute pieces as the collar itself." 



The thick collar was the edge of the peristome with its more or less regular supporting 

 plates as in any recent Crinoid. The mouth was placed within this peristomial space, and 

 the greater part of the convoluted organ would thus have lain altogether behind it. The 

 direction of its spiral is exactly the same as that of the digestive tube in Antedon or 

 Pentacrinus, as may be seen by comparing Dr. Carpenter's figure of the latter ^ (viewed 

 from above) and the " inferior end view " of the convoluted organ given by Meek and 

 Worthen." I believe that the gullet ran downwards and backwards as it does in 

 Pentacrinus ; and that the intestine, after following the convolutions of its support, 

 turned upwards again to end in the long anal tube, the so-called " proboscis." 



1 Eevision, part ii. p. 35. '" Paleontology of Illinois, vol. v. p. 329. 



3 Re\-ision, part ii. p. 35. * Patoontology of Illinois, vol. v. p. 331. 



5 Proc. Boy. Soc. LoncL, vol. xxiv. pi. viii. fig. 1. ° Palaeontology of Illinois, vol. v. pi. ix. fig. 125. 



