732 MR. P. H. CARPENTER ON THE [Dec. 19, 
applies it to denote the varying characters of the cirri; and I shall 
have much pleasure in employing it to this extent. His idea of dis- 
tinguishing Antedon and Actinometra by A and A! respectively is 
also a good one; though I should myself prefer A and a, as being 
less liable to printers’ errors. 
He gives formule for 58 species, 12 of which are MS. names of 
his own; but of the remaining 46 formule, no less than 12 would 
lead a collector who depended upon them for identification of a speci- 
men to form a false conception of the corresponding species. In 
the case of Act. parvicirra and Act. nove guinea, the error is but a 
slight one. But the formule given for Act. bennetti, Act. peroni, 
Act. schlegeli and other species denote a type of the genus which I 
have never met with, much less described; and were it not that I 
am now prepared for nearly any freak of nature among these 
animals, I should almost venture to call it a ‘‘ Comatulid impossi- 
bility.” 
Eight of these twelve species (including the three above men- 
tioned) have been described by myself in the ‘Notes from the 
Leyden Museum,’ vol. iii.; and as these Notes have a far less wide 
circulation than the Proceedings of the Zoological Society, it is 
necessary to prevent other workers from forming the wrong concep- 
tions of these types which would result from the exclusive use of 
Prof. Bell’s formule. 
The errors are in the parts of the formule which denote the cha- 
racters of the rays and their subdivisions, the remaining portions, 
which indicate the positions of the syzygies in the arm-bases and the 
characters of the cirri, requiring no alteration. As regards the for- 
mer, Prof. Bell says :— 
“If (1) we use the letters R, D, P for the radials, distichals, and 
palmars respectively, and insert them in the formula whensoever the 
respective axillary is a syzygy, we may (2) distinguish which of the 
first three brachials (one of which is, with but with very rare excep- 
tions, a syzygy) isa syzygy by simply making use of the number I, 2, 
or 3.... When a character frequently, though not always, obtains, 
the corresponding letter is put within brackets. ... When D or P 
appear in a formula it is clear the species must have more than 10 
rays’, because of the meaning of the words those letters represent ; 
where, however, neither distichals nor palmars present a syzygial 
joint, it will be necessary to make use of the mathematical sign for 
the square root to mark the fact of its being a multiradiate species” 
(pp. 531-532). 
’ Prof. Bell has here confounded the ten primary arms with the rays proper, 
by the division of which these arms originate. This has led him into much con- 
fusion, as will be pointed out later. According to Miiller, “ Radien nenne ich 
die auf dem Knopf aufgesetzten Stimme der Arme.... Auf jedem der 5 Kelch- 
radien sitzen 2 Arme, die entweder einfach bleiben oder sich noch einmal oder 
mehrmal wieder theilen.”’ (“ Ueber die Gattung Comatu/a, Lam., und ihre Arten,” 
Abhandl. d. Berlin, Akad. 1849, p. 240.) The arms therefore were clearly distin- 
guished from the rays by Miiller ; and it isa pity that Prof. Bell has confounded 
them, especially as in the genus Promachocrinus there actually are ten rays 
Springing directly from the centrodorsal. 
