280 THE VOYAGE OF H.M.S. CHALLENGER. 
life, is valueless. For individuals of Pentacrinus decorus have been found attached to 
telegraph cables by a spreading base ; and one specimen of Pentacrinus asterius at any 
rate, which I have seen, had the stem broken at a nodal joint, which was worn and rounded 
below, its central canal being closed up by a small median tubercle ; while this condition 
is common to several other Pentacrinide, as I have pointed out already (ante, pp. 18-22). 
Apart from the length of the internodes and the characters of the stem-joints, cirri, 
and arms, all of which are merely of specific value, the chief difference between 
Pentacrinus asterius and Pentacrinus decorus is in the mode of union of the two outer 
radials. In the latter type, as shown in Pl. XXXIV. figs. 3 and 5 (which were drawn 
under Sir Wyville’s own direction), these joints are united by a bifascial artieu- 
lation. But in Pentacrinus asterius (Pl. XII. figs. 18 and 21), and also in Pentacrinus 
miller’ and Pentacrinus wyville-thomson (Pl. XVIII. figs. 8, 11), there is a syzygy in 
this position. This difference, however, is one which occurs continually among the 
numerous species of the Comatulid genera. Antedon rosacea and Actinometra meridion- 
alis ave types of many species having the bifascial articulation; while Antedon fluctuans* 
and Actinometra solaris represent a smaller number of species which have the syzygy. I 
see no reason, therefore, for considering this difference as one of subgeneric value among 
the Pentacrinide, so as to separate Pentacrinus decorus, together with Pentacrinus blaker 
and Pentacrinus naresianus under a separate name, Neocrinus, from the other five species 
which have a syzygy between the two outer radials. Four of these, and probably 
Pentacrinus asterius as well, become free at a certain period of their life, just as Sir 
Wyville discovered to be the case in Pentacrinus decorus; so that one of the physiological 
characters on which he relied as giving Neocrinus an intermediate position between Penta- 
crinus asterius and the Comatulz is of much more general oceurrence than he supposed. 
The separation of Pentacrinus asterius and Pentacrinus decorus as types of sub- 
genera appears to have been abandoned by Sir Wyville within a year after he had proposed 
the name Cenocrinus for the former species. For in his well known memoir On the 
Embryogeny of Antedon rosaceus, published in the Philosophical Transactions for 1865, 
frequent reference is made to Pentacrinus (Neocrinus) asterias as well as to Pentacrinus 
(Neocrinus) decorus ; while Oersted’s species Pentacrinus miilleri was also referred to the 
subgenus Neocrinus. Sir Wyville seems, therefore, still to have regarded Pentacrinus 
briareus as having the first claim to the generic name Pentacrinus, although the Messrs. 
Austin had expressed an opposite opinion. He appears, however, to have eventually 
adopted their view, as all later writers have done. For in The Depths of the Sea 
reference is made to two West Indian species only, viz., Pentacrinus asterius and Penta- 
crinus miilleri ;? and neither Neocrinus nor Cenocrinus is mentioned, while Pentacrinus 
decorus is confused with Pentacrinus miillert. Subsequently also, when describing new 
1 The specific formula of this type is—A.R. 3.2.2. 2 . 
2 The Depths of the Sea, pp. 436, 442, 1873. 
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