262 THE VOYAGE OF H.M.S. CHALLENGER. 



associated by the Challenger in Prince of Wales Channel. No. 7, which is only No. 

 with palmar series, was found associated with it by the " Alert " both in Torres Strait 

 and in Prince of Wales Channel ; and in the latter locality No. 4 was obtained as well. 



This repeated occurrence of two or more varietal forms of Antedon variipinna in one 

 and the same locality recalls the fact, that of the five varieties of the protean Actinometra 

 parvicirra 1 which were dredged by Professor Semper among the Philippine Islands, 

 two occurred at Ubay and two at Bohol ; while examples of Pourtales' two species, 

 Actinometra pulchella and Actinometra alata, which I have been compelled to unite 

 under the former name, 2 were frequently found by the " Blake " to be living together at 

 the same locality in the Caribbean Sea. It is evident therefore that the cause of these 

 remarkable variations in one and the same specific type must be attributed to something 

 more than a mere change of local conditions. 



The single example of Antedon variipinna, var. 5, which was obtained by the 

 Challenger in Prince of Wales Channel, was serving as host to fourteen individuals of 

 Myzostoma, which Professor von Graff has referred to the following species — Myzostoma 

 dentatum, Myzostoma JUiferum, and Myzostoma quadriferum. The name of the host is 

 given in his Report 3 as Antedo n bidentata, P. H. Carpenter, this being the MS. name 

 which I had applied to the species before I became convinced of its identity with Antedon 

 variipinna, or had the opportunity of identifying it with Antedon decipiens, Bell. 



4. Antedon quinduplicava, n. sp. (PI. IV. figs. 1, a-d ; PL XLVII. figs. 4, 5). 

 Specifa formxda — A.3.2.y. 



Description of an Individual. — Centro-dorsal a thin disk, bearing about eighteen 

 cirri on its sloping sides. They have thirty tolerably equal joints, the last few rather 

 compressed, and faintly carinate ; the penultimate with a slight spine. 



First radials just visible ; the second rather closely united, forming a median 

 prominence with the pentagonal axillaries ; and there is a similar but less marked pro- 

 minence on the first two joints above the axillary. The rays may divide three times ; 

 three distichals with a syzygy, and two palmars without one. Sixteen arms of one 

 hundred and fifty or more smooth joints, all but the terminal ones being wider than 

 long ; the lower ones subtriangular and the later ones quadrate or almost oblong. A 

 syzygy in the third, and then between the eighth and fourteenth brachials ; others at 

 intervals of four to ten, usually seven or eight, joints. 



The distichal pinnule is about equal to that on the second brachial. That on the 

 third brachial is smaller again, while those on the fourth and fifth are both longer and 



1 Trans. Linn. Soc. Lond. (Zool.), ser. 2, 1879, vol. ii. pp. 52, 53. 



2 Bull. Mus. Comp. Zcbl., 1882, vol. ix. No. 4, p. 10. 



3 Zool. Chall. Exp., 1884, part xxvii. p. 17; ibid., 1887, part lxi. p. 7. 



