Report on the zoological collections made in the Indo-Pacific Ocean ...

;126 COLLECTIONS FROM MELANESIA.8. Linckia pauciforis.Martens, Arch.f. Nat. xxxii. (1866), p. 69.In only one example is one of the arms otherwise than perfectbut this does not seem to have been budded out in place of one castoff, but to have been bitten or broken off not far from its tip.Three dry specimens from Bird Island, N.E. Australia; coralreef.9. Linckia megaloplax.Arms five. R=67, r=9, or Il=7'5 r about. Adambulacralspines flattened, one for each plate, with blunted end ; externallyto and alternating with these are somewhat shorter papilliformspines ; the general granulation of the actinal surface of the diskextends between these latter; externally to them there is a row oflarger spines, the distribution of which is extremely irregular, forwhile at some points they are almost as closely packed as those ofthe more internal row, they are at others separated from oneanother by the distance of three or four of the inner spines. Therest of the abactinal siirface is closely covered with subequal granulesof some size. The abactinal surface is traversed very regularlyby six rows of poriferous spaces, which are comparativelylarge and markedly rectangular ; the smallest spaces are found inthe lowest row on either side ; a short distance from the tip of eacharm the spaces completely disappear, and the granulation becomesa little more prominent, and there is here, as in some allied species,a large specially modified plate with one or more large tuberclesupon it. The disk itself is covered with large pore-areas, and theonly noticeable character is the large and distinct, though not projecting,madrcporic plate. The pore-areas are about 2 milhm. wide,and the length of the madreporic plate, around which the granulesare very distinct, may be -1 millim. The colour of the abactinal surfaceis deep brown or black, whilst that of the actinal surface islighter.In a specimen smaller than that which has formed the chief basisof this description the two surfaces arc, towards the free end of thearm, distinguished from one another by the development of someshort marginal spines. In another, dried, specimen, intermediatein size between these two, the spines at the upper and lower marginsof the sides of the arm, though insignificant, are both largerand more numerous.The idea that the younger forms would have a larger supply ofspines is opposed by the fact that in a still smaller specimen thesespines are altogether absent *, while the skeletal plates are stouterthan in the specimens which bear the spines. The question nowarises as to whether there are three stages— («) one in which theossicles are so stout that no defensive spines are needed in addition(h) one in which growth has proceeded so rapidly that the bars of* Cf. Ann. & Mag. N. H. (5) viii. p. 441.