OCR Text |
Show 1882.] OR RARE SPECIES OF ASTEROIDEA. 123 MITHRODIA VICTORIA, n. sp. (Plate VI. figs. 3, 3 a.) R = 26-5, r = 3*5 ; R = 30, r = 4-6. Arms five, 4 or 4*2 millim. wide at their base, and not diminishing in breadth for some distance from the disk ; integument of the abactinal surface marked out into spaces by the arms of the calcareous skeletal pieces; a few spines, two or three millimetres long, are to be found along the middle line of the arm ; a few spines, which are generally a little longer, are placed at the upper or abactinal edge of the side of the arm. They frequently exhibit a white and brown patchwork-like coloration, which is due to the arrangement of the pigment in the integument which covers them. The actinal or lower margin of the side of the arm has along it from 7 to 10 spines of about the same length as those on the upper margin. The rather wide ambulacral groove is fringed by a regular series of short blunt spines, which are strongest in the region which falls within the disk. Within this series there is a row of smaller and more delicate spines, of which about five, set in fan-shape, belong to each ambulacral ossicle; the outer and larger spines may be coarsely granulated. The madreporic plate is small, white, and rounded, and is set not far from the centre of the disk ; the abactinal surface of the disk presents no characters by which it may be distinguished from that of the arms ; the papulae on the actinal surface are rare. N o pedicellariae detected. This new species is to be distinguished from M. clavigera by (1) the rarity of the papular spaces on the abactinal surface, (2) by the proportionally smaller spines, and (3) by the absence of a row of spines between the ventro-marginal series and the abactinal rows, a row which appears to be constantly present in the better-known form. Judging from the single specimen of M. bradleyi in the collection of the British Museum, that species has much larger papular pores, has two rows of spines on the actinal surface of the rays, and none at all on their abactinal surface. Victoria Bank (20° 42' S., 37° 27' W . ) ; depth 39 fathoms; bottom, dead coral. Both the specimens from which the above description has been drawn up are injured; one appears to have lost one of its arms during life, as the free end is healed. They formed part of the collection made by Dr. Coppinger (H.M.S. 'Alert') in 1879-80; but they were not noticed in m y report (P.Z.S. 1881), as they did not form a part of the fauna of the Straits of Magellan. FROMIA INDICA. Fromia indica, Perrier, Rev. des Steller. p. 177. Scytaster indicus, Perrier, Ann. Sc. Nat. (5)xii. p. 255. Although M . Perrier's description states that his specimen has six rays, I have no hesitation in assigning to the species a five-rayed specimen, in which the proportion of R to r is somewhat greater than in the example which formed the object of M . Perrier's description. I base the determination chiefly on the following considerations : - T h e presence of six rays is of itself no evidence in favour of a true polyactinid condition as against a possible heter- |