138 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
very low down in the sac (Plate VII. Fig. 1a). 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 VII. Figs. la, 24,6, 3, 4, 7, 8). There are other Poteriocrinide, 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 Auwlocrinus 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 Ichthyocrinide has been observed only in Zaxocrinus and 
Onychocrinus (Forbesiocrinus 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 Zaxocrinus and Onychocrinus are derived from the asymmetrical Gnori- 
mocrinus, Which apparently had a similar tube. The arrangement of the 
anal plates in the Ichthyocrinidx is substantially the same as in the Fistu- 
lata. In some of their genera only the plate « is represented, in others A’ ; 
while still others have no anal plate at all. Bather makes no reference to 
the anal plates of the Ichthyocrinide, 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 must 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 with the anals of the 
Ichthyocrinide, among which interbrachials are represented. But what 
would be the result? Some of their genera have interbrachial plates, and 
