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Show 80 PROF. F. J. BELL ON THE [Feb. 19, racters. He speaks, for example, of the difference of the form of the body between N. armata and anv species of the genus Oreaster, as he regards it. But a comparatively insignificant difference in the value of - is not even a subgeneric character. The second point of r . difference is, in Prof. Perrier's words, " le peu de saillie des ossicules dorsaux qui sont a peine distinctes," but they are, at any rate, just as clear as they are in O. granulosus, and, indeed, they are much more so, while there are specimens of 0. gracilis in which the lophial line is no more distinct. M . Perrier proceeds, "Les aires poriferes sont larges, confluentes et paraissent m e m e parfois envahir toute l'eten-due du disque." In young specimens the poriferous areae are much more distinctly marked off than in O. alveolatus ; if there is any disadvantage to the side of O. armatus with respect to its alveo-lation, when adult, it is no doubt to be correlated with its better development of long defensive spines. It is not always the case that the spines of species of true Oreasters, according to M . Perrier- take, for example, his own species 0. alveolatus-are always free of granules at their tip ; we find so many intermediate stages between a complete investment and an almost complete absence of granules that this character, again, must not be regarded as having, at the utmost, more than a specific character. The species m a y be defined in the following terms:- R = l * 7 r to 2*1 r. Disk not high, arms very short, interbrachial angles rounded ; lophial and apical spines very strong, intermediate spines and spines on marginal plates exceedingly well developed ; spines likewise developed on the ventral plates. Nine plates in the supero- and nine in the inferomarginal series; the latter all bear spines, which are short in the angles and of a moderate size near the distal ends of the arms ; the three or four spines found on the distal plates of the superomarginals are m u c h larger ; the superomarginals are greatly elongated from above downwards in the angles of the arms, where they almost shut off the inferomarginals from any share in forming the sides of the arm ; further out the plates become shorter, but the penultimate is very large and convex. Ambulacral spinulation diplacanthid ; three or four fairly developed spines in the lower, and one much larger in the outer row. The ventral ossicles covered with rather coarse granules, and each having, rising from its centre, a blunt stout spine; some large valvular pedicellariae are developed on these plates; the granules on the inferomarginals are only a little less coarse than those on the ventral ossicles, but the greater number of those on the superomarginals are much more delicate; pedicellariae are only feebly developed. With increasing size the boundaries between the poriferous areae become largely obliterated ; just at the interradial angles, however, the ossicles are stouter in older than in younger specimens. The lophial spines are strong and sharp in the adult; between them some few spines m a y become developed ; and in the centre of the apical region there is a spine as long or nearly as long as the apical. A few pedicellariae are developed on the dorsal surface, the |