130 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
various families, we find in the Batocrinide directly above the plate x a 
supplementary anal, and an interbrachial at each side of it, exactly as in 
most species of Cyathocrinus and Dendrocrinus, except that the interbrachials 
of the two latter — 7. e., the plates corresponding to them — are incorporated 
into the tube, but those of the Batocrinide into the cup. Turning to the 
Actinocrinidx, the plate x supports a supplementary anal in the second inter- 
brachial row, but none in the first, a structure recurring in Graphiocrinus, 
in which z is followed by two tube plates which take the place of the two 
interbrachials of Actinocrinus. In the Dolatocrinites, however, in which z is 
wanting, and the first row of the anal interradius is formed of a single plate, 
this rests upon the sloping faces of two radials, thus occupying almost the 
same position as the plate ¢ (2 of Bather) in Eetenocrinus, Hybocrinus, and 
Tocrinus. That the plate ¢ in some of these forms is somewhat irregular in 
position, leaning more to the right than to the left, is due to the asymmetry 
of the right posterior radial. 
From these observations it appears that there is a close agreement be- 
tween the anal plate and tube plates of the Fistulata on one side, and the 
anal plate and interbrachials in the cup of the Camerata on the other; and 
we are led to believe that those plates respectively are homologous. Admit- 
ting this, we have a much more satisfactory explanation of the anal plates of 
the Fistulata than that given by Bather, whose views are totally at variance 
with the structure of the Camerata, and are based upon premises which are, 
to say the least, hypothetical. 
After agreeing upon the structure of Dendrocrinus and Jocrinus, that of 
the other Fistulata is readily understood. Anomalocrinus is in a condition 
similar to that of Jocrinus, but it has two compound radials instead of one 
(Fig. 12). The plate x is unrepresented, and the tube, which is narrow, 
rests within a notch formed by the sloping upper faces of the two posterior 
radials. Nearly the same structure is found in Heterocrinus and Hetenoerinus 
with three compound radials, and in Hybocrinus with but one, and in all of 
them the plate « is wanting. How Mr. Bather could conclude from the 
structure of Hetenoerinus, Iocrinus or Hybocrinus, three of the most primitive 
forms, that 2 originated as a plate “ morphologically corresponding to an 
ordinary brachial,” and that ¢ could sink down to the basals, we do not 
understand. It appears from his own diagram that the plate which he calls 
« in Ectenocrinus is placed symmetrically between the two posterior radials, 
resting as much on the one plate as on the other, but not touching the basals. 
