KEPOET ON THE CEINOIDEA. 265 



Bell's first formula for Antedon elegans 1 indicated that it had three distichals and 

 sometimes three palmars, with syzygies in the axillaries ; and I classified it accordingly. 2 

 His subsequent description 3 of the palmars says, however, that "if the arms divide 

 ao-ain there are generally two joints, when the axillary is not a syzygy ; but there may 

 be three joints, and then the axillary is a syzygy." His figared specimen has four 

 palmar series of two joints and one of three joints, and he gives the specific formula as 



including both varieties |A.3.pr.~). This is all very well in cases where two palmars 



occur on the outer, and three on the inner arms of the ray, as in Actinometra nobilis 

 (PI. LXV. fig. 1), but if it is done in every case where the arm-divisions are not quite 

 regular, the formulae would become so complex that we should do better without them. 

 It is extremely rare for any tridistichate Comatula to have its secondary and subsequent 

 arm-divisions all exactly uniform ; and sometimes, as in Actinometra parvicirra (PL 

 LXI. figs. 1, 5), there is the same variation in the distichal series. Hence all that we can 

 do is to go by the majority of the distichal or palmar series respectively ; and as Bell 

 recognised this fact by omitting any mention of the two-jointed palmar series in 

 Antedon microdiscus, I wonder that he thought it necessary to refer to the abnormal 

 three-jointed series in Antedon elegans. His formula also omits any reference to the 

 post-palmar series which occur on one of his specimens. 



The corrected formula for Antedon elegans thus becomes A.R.3.2.(2).— , which is 



exactly the same as that given above for Antedon Jluctuans ; and the two species are 

 in fact identical. Under these circumstances the type must be known for the future as 

 Antedon elegans, Bell, although its most important distinctive character was omitted in 

 his diagnosis. It is noteworthy that of the three examples obtained by the " Alert " at 

 Port Molle, one is very considerably different from the other two, both in colour and in 

 the amount of serration of the arms ; while the Challenger's dredgings at Station 190 

 yielded four examples of the same type, three alike and one different. 



The "Alert" found an intermediate form in Torres Strait; Semper's Philippine 

 collection contains representatives of the type ; and I have lately found a most valuable 

 series of varying forms of this species among the Comatula? dredged by Dr. Anderson 

 in the Mergui Archipelago. In these last, as in the examples obtained by the " Alert " 

 and Challenger, the ambulacra of the disk are very strongly plated, and also the inter- 

 palmar areas at their sides, though this is less marked in the Philippine variety. I find 

 the same extensive plating on the disk of another species from Mergui which has a 



syzygy between the two outer radials and a formula A.R.2.2.2.y. It thus differs 

 altogether from Antedon elegans, Antedon multiradiata, and Antedon microdiscus in 

 having but two articulated distichals, instead of three, with a syzygy in the axillary. 



i Proc. Zool. Soc. Lond., 1882, p. 534. 2 Ibid, pp. 746, 747. 3 " Alert" Report, p. 162, pL xiii. fig. B. 



(ZOOL. CHALL. EXP. — PART LX. — 1887.) OoO 34 



