1882.] PROF. F. J. BELL ON THE COMATULID^. 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 cloture. 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 Echinoderniata. 



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 Comatulidse, 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 palmai-s ; while the separate joints after the final division are 

 known as the brachials. 



(2) The leading differences between these sets of joints indifferent 

 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 exceptioas, a 

 syzygy) is a syzygy by simply making 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 more 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, b, and c to represent (ew, 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 be. 



Antedon and Actinometra may be usefully, though not of ne- 

 cessity, distinguished by making A or A' part of the formula. 



One or two examples will explain the aim of this note. If we have 

 a ten-rayed Antedon with 1 5 cirri of 40-50 joints, with its first syzygy 



on the third brachial, we may write its formula thus, 3 A - ; so, again> 



