| OCR Text |
Show 1881.] THE SURVEY OF H.M.S. 'ALERT.' 99 ASTROPHYTIDA. The two specimens of this group which were received from tne Straits of Magellan belong to the genus Astrophyton ; and both appear to be representatives of a species hitherto undescribed. So far as I know, the only species which has yet been recorded as coming from the same region is the A. pourtalesi of Lyman, which was obtained off the eastern coast of Patagonia1 during the Hassler Expedition. The species now to be described falls into the same group as it, belonging, as it does, to the series which, as Prof. Lyman has shown, is characteristic of the temperate seas, and in which the forkings are, as compared with such forms as A. muricatum, few and distant. ASTROPHYTON LYMANI, sp. n. Radial ribs prominent, compressed laterally, their narrow ridge with short conical or rounded spiniform processes ; somewhat similar spines are found in medium quantity projecting from the thick brown skin of the interradial spaces. Madreporic body single, large ; the tentacle-scales extend nearly as far as the mouth, and soon become arranged by fours in each transverse row. The following are the more important measurements :-Diameter of disk 45 millims. ; breadth of arm within disk 7'5 millims.; breadth of arm just without disk 6 millims. ; greatest width of madreporic body 4"5 millims. ; genital slits 4 millims. long. millim. Distance from mouth to 1st fork 15 "5a „ „ 1st to 2nd „ 15 „ „ 2nd to 3rd „ 21 „ „ 3rd to 4th „ 25 ,, „ 4th to 5th „ 23 „ „ 5th to 6th „ 28 6th to 7th , 36 163-5 There are ordinarily two terminal branches of no great length. The mouth-parts are all simple, spiniform, and rather numerous. The madreporic body, which in the specimen under description is broken up into several parts, is placed quite in the apex of the in-terbrachial angle, so that it is almost semilunar in form ; in the dry example, at any rate, it is quite easy to distinguish. The inner lip of the genital slits is fringed with a few spines or spinous granules. The dark-brown interradial spaces on the actinal surface contain, except at their peripheral margin, a considerable number of small white granules, and they are separated from the corresponding space on the upper surface by a white calcareous band, altogether similar to the band which forms the base of the radial triangular space, and, like them, provided with some short blunt or conical projections; 1 111. Oat. M . 0. Z. viii. 2, p. 28. 2 Greatest length always given. 7* |
