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- Mechisce) 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 chai'acter, 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 XIII. figs. 3, 5, 8), just as in Pentacrinus decorus 

 (PI. XXXVI.; PL XXXVIL 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 tke 

 " 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 Penta^ririus 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 Pentojcrinus 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 



I Sea Lilies, Tlu: Intellectual Observer, August 1864, p. 7. ' Ibid., p. 10. 



3 Proc. Boy. Soc. Edin., vol. vii., 1872, p. 760. * Sea Lilies, The Intelleciual Observer, August 1864, p. U. 



