REPORT ON THE CRINOIDEA. 279 
Wyville in 1864,! the type being a new West Indian species which he designated as 
Pentacrinus (Neocrinus) decorus. The differences between this type and Pentacrinus 
asterius (caput-Meduse) are undoubtedly considerable, as I have expressed by separating 
the two as far as possible in my arrangement of the species (see p. 299). But they are rather 
physiological than morphological in character, and one or two errors of observation have 
caused them to appear greater than they really are. There are syzygies below the nodal 
joints of Pentacrinus asterius (Pl. XII. figs. 3, 5, 8), just as in Pentacrinus decorus 
(Pl. XXXVI; Pl. XXXVII. figs. 5-8, 12, 19, 21); so that although the stem of the 
former species is very strong and rigid, it can hardly be said to be distinguished by the 
“absence of all provision for its rupture,” such as Sir Wyville* described in the more 
slender stem of Pentacrinus decorus. 
The supposed difference between the disks of Pentacrinus asterius and Pentacrinus 
decorus, which was founded on a belief in the presence of tooth-like oral plates in the 
former genus, is also due to error, owing to the unsatisfactory condition of Michelin's 
specimen, which was said to possess these embryonic structures. Sir Wyville recognised 
this subsequently when he obtained a spirit specimen of Pentacrinus asterius, the disk 
of which he described as follows : *—‘ The perisome of the disk is covered with irregular 
calcareous plates, and at the free inner angles of the interradial spaces these plates become 
closer, and form a solid kind of boss; but there are no distinct oral plates.” On the 
other hand, the disk of Pentacrinus decorus* (Pl. XXXIV. fig. 2) could hardly be 
called “comparatively unprotected” as distinguished from that of Pentacrinus asterius, 
which Sir Wyville described on the previous page as “uniformly defended and plated 
with calcareous pavement.” 
In the nature of the arms, however, there is a considerable difference between the two 
types, as was well described by Sir Wyville. Those of Pentacrinus asterius are “ greatly 
multiplied, large and strong. No syzygies, save those at the base, which can be used on an 
emergency, tend to diminish their strength, an arrangement essential to the full supply 
of food in their fixed condition.” On the other hand, in Pentacrinus decorus the number 
of arms is “greatly less, and the arms are provided throughout with syzygies, an 
arrangement apparently suitable to its greater liability to trivial accidents in its free 
condition.” He went on to say, “ At first I had some doubt as to the propriety of making 
this species the type of a new subgenus, and any one of the above characters would 
certainly not have afforded sufficient grounds; but all these characters taken together 
form a remarkably compact assemblage, which places Neocrinus in a directly intermediate 
position between Cenocrinus and Comatula.” Two of the principal points of difference 
between Cenocrinus and Neocrinus have, however, no foundation in fact, while a third 
is, at most, one of specific value ; and the fourth, the supposed difference in the mode of 
1 Sea Lilies, The Intellectual Observer, August 1864, p. 7. * Ibid., p. 10. 
3 Proc. Roy. Soc. Edin., vol. vii., 1872, p. 766. 4 Sea Lilies, The Intellectual Observer, August 1864, p. 11. 
