738 MR. p. H. CARPENTER ON THE [DcC. 19, 



veniently described as consisting of distichal joints. But in order 

 to avoid misconception, I expressly inserted the word distichals in 

 speaking of the first division of the rays of Act. pulchella '. The 

 description of this species was written before those of the Leyden 

 ComatulcB, and must have been read by Prof Bell, as he gives a for- 

 mula based upon it. 



I cannot help suspecting, however, from the formula which he 

 gives for Act. alternans, that he has thus misunderstood my meaning. 

 It is as follows, SA'RPP"?. This can only be interpreted in the 

 following way : — that the radial axillary " is a syzygy " (which is not 

 the case) ; that there are two distiehals", the axillary without a syzygy 

 (while there are really three, the axillary with a syzygy) ; that there 

 are two or three palmars, the axillary with a syzygy (while there are 

 really two, the axillary without a syzygy) ; and so on for the two re- 

 maining divisions, so that the formula should read 3 A'DP'P'"^. Even 

 then, however, it would not indicate whether two or three distichals 

 are present ^ nor whether there are one or two palmars, nor the 

 number of joints in the two remaining divisions ; so that one would 

 be entirely at a loss as to the systematic position of t he type. 



Prof. Bell gives the formula for Act.japonica as \/3 A'R ?. Even 



after the removal of the unnecessary and totally misleading R, the 

 formula is entirely incorrect as regards the ray-divisions, and says 

 nothing about any palmars being present. It means that there are 

 two distichals, the axillary not a syzygy* But in Miiller's classifi- 

 cation this species is placed in a group distinguished as follows, 

 " Die Axillaria der Arme mit Syzygien ; " and my own description 

 runs, " Primary and secondary arms each of three joints, the axillary 

 a syzygy," or, as Prof. Bell puts it, " Three distichals and three 

 palmars, the axillaries syzygies." His formula should therefore 

 be3A'DP|. 



The formula which he gives for Act. parvicirra (SA'DP — ) 

 implies that palmars are always present on some of the rays. A 

 specimen has been figured, however, with 13 arms only, having 

 distichals on only three rays and no palmars at all ; and others have 

 been noticed with but 18 and 20 arms *. The P should therefore be 

 put within brackets, and the formula stand 3A'D(P) (— , like that of 

 Act. wahlhergi, MnW., and Act. varinhilis, Bell, MS. 



In like manner the formula given for Act. peroni (^SA'RDPr^ 

 does not convey the information that there may be another axillary 



^ Bull. Mus. Comp. ZooL vol. ix. no. 4, p. 10. 



^ I am at a loss to understand how Prof. Bell can have supposed that the 

 second joint after the radial axillary, which is described as bearing a pinnule, 

 can at the same time be an axillary joint ; but no other types without a syzygy 

 in the axillary than a series of two distichals have yef been described. 



^ I. e. vmless the rule be known that if the distichal axillary is a syzygy it is 

 always the third joint, and not the second, as may sometimes be the case with 

 the palmars. 



* Trans. Linn. Soc. 2nd series, Zool. vol. ii. 1879, p. 44, and pi. ii. fig. 9. 



