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Show 1894.] ECHINODERMS OF MACCLESFIELD BANK. 399 Arms about 100 mm. long; diameter of disc 10 mm.; length of cirri up to 28 mm. Macclesfield Bank, 31-36 fms. H.M.S. ' Penguin.' ANTEDON BASSETT-SMITHI, sp. nov. (Plate XXIV.) This is one of the late Dr. H . Carpenter's spinifera-group, and belongs to that section in which there are from fifteen to twenty-five cirrus-joints. The cirri are not arranged in definite rows, and the sides of the distichals are not flattened. Centrodorsal rather large, slightly hollowed in the centre, which is bare of cirrus-pits ; the cirri in three planes at tbe side, about forty in number, with from twenty to twenty-five joints, some of which are considerably elongated ; in the distal half they have a slightly projecting free edge, but there is no distinct spine. Arms, probably, more than forty in number, stout, widely separated at their bases, where the disc-incisions are deep. Pirst radial obscured, the secoud wide, the third almost triangular; two distichals, two palmars; the latter may or may not be united by syzygy. In the syzygies of the arms the most extraordinary variations occur : sometimes the first two brachials are united by syzygy, sometimes (to use the usual terminology) the third is a syzygy, sometimes both first and second and third are. The first arm-joints are squarish, the succeeding alternately wider and narrower on either side. The second and third pinnules ordinarily have the two basal joints much wider than the rest and of a characteristic shape (Plate X X I V . figs. 5 & 6); none of the pinnules are either stout or long. I must confess that I am quite at a loss to know how to explain the extraordinary divergencies exhibited by the syzygies of this species. It is, of course, a great pity that there is only a single example ot it, and it would be rash to say that it destroys the generalizations to which long study of a number of species and specimens led Dr. H . Carpenter; but, on the other hand, it cannot but shake our belief in the universality of the conclusions drawn up by Carpenter on pp. 44-46 of the ' Challenger' Beport on the ' Comatulae.' If it be merely an abnormality it is a case in which monstrosity is really carried too far, and is one that is, probably, quite unequalled by any known Crinoid. So far as I know, and, indeed, so far as I can, after diligent search, discover, the only recorded case of striking irregularity in the position of the syzygies is that of the Grdttingen specimen of Antedon ma-cronema, of which Dr. C. Hartlaub remarks l:-" Bemerkenswerth ist an ihui die unregelmassige Lage der ersten Syzygie, die zwischen dem 3. 4. und 6. Brachiale wechselt." But here we have not only two conditions which have been supposed to be mutually exclusive in different arms of one specimen, but these very two conditions occur on one arm. Did we know something of the function of the syzygies, it would be easier to come to a decision, but as our knowledge of that function appears to be summed up in the state- 1 Nova Acta Acad. Cses. L.-C. lviii. no. 1, p. 78 (Halle, 1891). |
