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Show 260 PROF. F. J. BELL O N [Mar. 14, How is one less qualified than either of these two observers settle a question on which they, with their ample knowledge, are divided ? I, at any rate, pretend to no right or authority, but, as I have to assign the specimens to a systematic place in a list of Asteroidea which I am now preparing, it may be permitted to say why they are to be found with the Archasteridae. If we take the definitions offered us in the Introduction to the Report on the ' Challenger' collection of Starfishes, we find we might place Odontaster almost indifferently with either Archasteridae or Pentagonasteridae, though there is a slight balance in favour of the former. If we take M. Perrier's latest revision of his scheme of classification, there can be no doubt that the definition of the order Paxillosae1 (op. cit. p. K.71) applies to Odontaster very much better than does the definition of the Valvulatae ; and the Pentagonasteridae belong to the latter, the Archasteridae to the former of these two orders. But at this point I must stop or I shall be drawn into a discussion as to the classification of the subdivisions of Asteroids, which would be far too lengthy for me just now. Only let me point the moral that the present state of the classification of Asteroids is not as satisfactory as one would hope to find it after the labours of two industrious zoologists for five or more years, and that Odontaster is sufficient to prove that no classification can be satisfactory which allows of a wide gap between the Archasteridae and the Pentagonasteridae. A list of the species of Odontaster with the synonyms may be useful. ODONTASTER. Odontaster, Verrill, Am. J. Sci. xx. (1880) p. 402. Gnathaster, Sladen, Chall. Rep. Ast. (1889) p. 285. Asteroclon, Perrier, Miss. Cap Horn, Echinodermes (1891), p. K. 132. 1. ODONTASTER BELLI. Pentagonaster belli, Studer, Anhang zu Abh. k. Akad. Wiss. Berlin, 1884 (1885), p. 31. Prof. Perrier thinks this may be a synonym of Odontaster singu-laris, but the ventral plates of that species are in no way paxilli-form; tbe adambulacral spine of 0. belli appears to be specially modified, and in the distal fourth of the arm the intermediate actinal plates are wanting, For these reasons separation appears to be, at present, the safe course. 2. ODONTASTER DILATATUS. Pentagonaster dilatatus, Perrier, Arch. Zool. exper. v. (1876) p. 33. Gnathaster dilatatus, Sladen, Chall. Rep. Ast. (1889) p. 750. 1 M a y I take this opportunity of remarking that " paxilli," and not " paxills," is the correct form of the name of these plates ? |
