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Show 1894.] ECHINODERMS OF MACCLESFIELD BANK. 407 oval. Twelve mouth-papillae to each angle of the jaw; a single row of large granules between them and the triangular mouth-plate. Upper arm-plates oblong, much wider than long; the lower have their distal ends much encroached on by the side-plates ; the spines are quite stout, and the lowest is long enough to reach the free edge of the plate next in front. Colour, when dried or in spirit, pale brown, with eight or nine rings of a yellowish hue at distances along each arm ; bands or patches of a yellowish colour on the disc. Diameter of disc 7 m m . ; 6 ; 5. Length of arm 60-5 m m . (broken a little); 60 (ca.) ; 50. Macclesfield Bank, 13-35 fms. OPHIOTHRIX. As may be supposed, there were a large number of examples of this genus in the collection; how many species are represented it is quite impossible to say, but I have determined twelve with very great difficulty. M y experience in this particular is, however, no different to that of any other zoologist who attempts to name specimens of this remarkable genus-unless, indeed, he be one who has no knowledge at all of its peculiarities. N o one who has dredged our common British Ophiothrix, and has seen how varied are its colours and the characters of its spinulation, will attempt to name exotic specimens with a light heart. It would, of course, be easy enough to do so if one were to take no note of the experience gained by a study of British specimens, for with a few specimens one can always make new species. With considerations such as these before me, it will be no matter for wonder that I have refrained from describing any " new species " from the present collection. To confess the whole truth, I had intended to make an exception in favour of a remarkably coloured and fairly well represented species from Macclesfield Bank. When, however, it was compared with 0. purpurea, with which, indeed, I had at first no idea of comparing it, I found that the new specimens and the old so intergraded that there could be no doubt they were one and all members of an almost protean species. It would be worth the while of a student with unlimited leisure-and less, I fear, will hardly do-to work out large series of Ophiothrix. In saying this I should like to add that the late Dr. Brock made a very useful beginning in his essay on " Die Ophiuridenfauna des indischen Archipels"1. It has sometimes been supposed that colour is a good guide in the identification of species of this genus. Thus no less an authority on Ophiuroids than Dr. Liitken writes:-"Le systeme general de coloration constitue un caractere important qu'il ne faut pas negliger dans la distinction specifique des Ophiothrix "2. Or, if I may trust myself to translate the fuller Danish text, 1 Zeitschr. f. wiss. Zool. xlvii.; see especially pp. 511 & 516. 2 Danske Vid. Selsk. Skrift. viii. (1869) p. 104. 27* |