44 THE VOYAGE OF H.M.S. CHALLENGER. 
Pentacrinidz and Comatule ; and I see no reason to believe that the minute interradials 
of Reteocrinus are in any way different from those of the Neocrinoids. But I regard 
them as perisomic plates continuous with those of the disk above, which was in no sense 
a “vault” like that of the Actinocrinide. Meek’s figure of Reteocrinus nealli! 
illustrates this point admirably, and after examining disks like those of Pentacrinus 
wyville-thomsoni, Pentacrinus alternicirrus, Pentacrinus naresianus, and Pentacrinus 
mollis, together with similar disks in numerous Comatulee (Pl. XVIL fig. 6; Pl. XXVI. 
figs. 1, 2; Pl. XXX. fig. 2; Pl XXXIIT. fig. 7; PL LEV, fie. d0ic¢o Ph LV.) eamdaleo 
(thanks to the kindness of Mr. Wachsmuth) that of Reteocrinus nealli, I find it difficult 
to believe that the so-called vault of Reteocrinus was anything but the true oral surface 
of the animal. 
Miller's genus Xenocrinus’ is in this respect essentially similar to Reteocrinus. 
“The azygos area is remarkably large and covered in the central part by a vertical series 
of plates having about the same size as the regular radial series; and upon each side of the 
vertical series there is a depressed area covered by small plates having a tubercle in the 
central part, as in the regular interradial areas. There are seven plates, each having a 
length about twice as great as its width, in the vertical series, from the basal plate, upon 
which the series rests to the top of the vault. This vertical series is continued to the 
top of the proboscis, and contains in its entire length more than fourteen plates. It has 
such strong resemblance to the radial series, except as to the branching at the secondary 
radials, that the general appearance of the body is that of a species having six radial 
series.” Miller figures the specimen with fourteen plates in the vertical series, and 
remarks that we learn from it that “the proboscis extends as high as, and probably 
beyond the extremity of the arms.” He also says that the small plates between the rays 
and their subdivisions “ continue over the margin of the vault, and undoubtedly cover it, 
and also more or less of the long proboscis.” I do not see, however, that this so-called 
but unknown proboscis is anything more than an anal tube covered by perisomic plates, 
asin Letracrinus and so many other Neocrinoids. I also doubt whether Miller is right in 
stating that the vertical series is continued to the top of the proboscis, for (to judge from 
his figures) he does not seem ever to have met with a specimen perfect enough to show 
the top as it is shown in Meek’s figure of Reteocrinus nealli.® But I think it quite 
possible that, considering the size of this vertical series, it may have become free at the 
top of the calyx as the anal appendage of Thawmatocrinus does (Pl. LVI. figs. 4, 5), 
instead of tapering away quickly and ending on the lower part of the anal tube as in 
Reteocrinus nealli. 
The ventral sac or proboscis of Cyathocrinus is usually much larger and more 
1 Paleontology of Ohio, vol. i. pl. ii. fig. 3c. 
* Description of some New and Remarkable Crinoids and other Fossils of the Hudson River Group, Journ. Cine. Soc. 
Nat. Hist., vol. iv. pp. 72, 78, pl. i. fig. 3; pl. iv. fig. 6. $ Paleontology of Ohio, vol. i, pl. ii. fig. 3c. 
