1882.] PROF. F. J. BELL ON THE COMATULIDZ. 531 
If science is not to be overwhelmed by literature, an alternative is 
only to be found in such abbreviation as the mathematician, the 
physicist, and the chemist have already adopted, or in some form 
of the modern weapon, the cléture. It is unnecessary to insist on 
the advantage of the former. 
Recognizing the force of these considerations, I proposed last year 
to this Society a method of formulating the results attained to, as 
regards our knowledge of the specific characters of the members 
of the genus Asterias. For the purpose of extending the process 
as much as possible, I select on this occasion a different group 
of the Echinodermata. 
I cannot pass directly to the subject without expressing my 
satisfaction with the knowledge that Dr. Vosmaer, of Leyden, has 
invented a kind of short-hand for the description of Sponges, 
which will, I hope, bring him before long to a system of formu- 
lation. 
When we make a general survey of the two genera which contain 
by far the greatest number of the Comatulide, Antedon and Acti- 
nometra, we note that, 
(1) As a general rule, the arms are ten in number or more than 
ten; the joints before the first division are called radials, those 
before the second distichals; if there is a further division we shall 
have palmars ; while the separate joints after the final division are 
known as the drachials. 
(2) The leading differences between these sets of joints in different 
species are to be found in the varying arrangement of that mode of 
union to which Johannes Miiller applied the term syzygial. 
(3) The cirri on the centrodorsal vary in number, and in the 
number of their joints. 
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 very rare exceptions, a 
syzygy) is a syzygy by simply makiug use of the number 1, 2, or 3. 
Thirdly, the cirri and their number may be thus formulated : if there 
are from 1-12 cirri, we may say there are few; if from 12-30, a 
moderate number ; and if more than 30, a large number: if there are 
not mure than 20 joints to the cirri we may look upon them as being 
few, if from 20-40 moderate, and if more than 40 numerous. I 
propose to use the letters a, 6, and ¢ to represent few, moderate, 
and numerous respectively ; while the letter for the number of cirri 
will form the numerator, and that for the number of joints the 
denominator of a fraction; and where there is a difficulty of decision 
one might write ab or de. 
Antedon and Actinometra may be usefully, though not of ne- 
cessity, distinguished by making 4 or 4! part of the formula. 
One or two examples will explain the aim of this note. If we have 
a ten-rayed dntedon with 15 cirri of 40-50 joints, with its first syzygy 
on the third brachial, we may write its formula thus, 3 A . 3; SO, again, 
