138 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



very low down in the sac (Plate YII. Fig. 1 a). An anal pyramid has never 

 been found in place in this family, but that it existed, at least in some of the 

 species, seems very probable from the form and large size of the opening 

 (Plate YII. Figs. 1 a, 2 a, b, 3, 4, 7, 8). There are other Poteriocrinidce, and 

 especially among species with an inflated, balloon-shaped sac, which have no 

 openings in the sac, and we are inclined to suppose that in these cases, and 

 also in many other Fistulata, the anus was located in the disk proper between 

 the sac and the mouth. In the remarkable Aulocrinus represented on Plate 

 VII. Fig. 9, there is a large spout-like tube passing out from the huge sac 

 between the arms on the anterior side, half way down, like the simple 

 opening in Figs. 7 and 8. We have found this extraordinary tube pre- 

 served in five other specimens of this species, and its form and position 

 are very constant. 



The anus of the Ichthyocrinidae has been observed only in Taxocrinus and 

 Onychocrinus {Forhesiocrinus de Kon. and Le Hon). Both genera have a small 

 tube, of which the posterior side consists of a vertical row of subquadran- 

 gular, comparatively large plates. Its anterior side is composed of a large 

 number of very minute pieces, forming a kind of pouch, widest at the 

 proximal end, which gradually passes into the disk. At the anterior side 

 the tube leans considerably to the right, and it may be suggested from this 

 that Taxocrinus and Omjchocrinus are derived from the asymmetrical Gnori- 

 moerinus, which apparently had a similar tube. The arrangement of the 

 anal plates in the Ichthyocrinidae is substantially the same as in the Fistu- 

 lata. In some of their genera only the plate x is represented, in others B' ; 

 while still others have no anal plate at all. Bather makes no reference to 

 the anal plates of the Ichtliyocrinidse, but regards the anals of the Camerata 

 as morphologically distinct from those of the Fistulata. On page 319 

 {op. cit.) he says : '^ it may be pointed out that, as interradials do not 

 enter into the composition of the dorsal cup in any Fistulata, none of 

 these plates can well be the homologues of interradials : in many of the 

 Camerata actual interradials are present in the anal area, but in the Fis- 

 tulata at least we mnst look elsewhere for the origin of the so-called 

 ^ anal ' plates." Now if it is true that the anals of the Camerata re- 

 present something different from those of the Fistulata, because they 

 possess no interbrachials, it must be the same also w^ith the anals of the 

 Ichthyocrinidae, among which interbrachials are represented. But what 

 would be the result? Some of their genera have interbrachial plates, and 



