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Show 430 PROF. F. J. BELL ON THE TEMNOPLEURIDAE. [June 1, enormous abactinal system, its comparatively large anal area, and its small rounded actinostome with a thin complete edge. The following measurements of the specimens from Bondy Head and "Portugal" may be compared with those given by much younger and by intermediate specimens. Bondy Head... Station 188 ... Station 186 a.. Station 186 fi.. Absolute diameter in millims. 74 64 22-5 14 9 Percentage value of Height. 66 60 53-3 57-14 Abactinal area. 19 2109 22-2 21-4 Anal area. 9-86 101 111 Actinostome. 22-19 21-9 31-6 321 33-3 It is obvious from the above figures that the most marked changes occur in the actinostome, which, almost large in the young, becomes so small in the well grown forms ; and it is interesting to compare the change with what obtains in Temnopleurus. T. toreumaticus has the actinostome even proportionally larger when young ; but its adult specimens (50 millims. in diameter) present a percentage value for their actinostome of as much as 26, the relation between the young Salmacis and the adult Temnopleurus being, even in the character of the actinostome, not obscurely indicated. The following points may also be noted in the young specimens:- The lozenge-shaped patches are not yet apparent; the sutural pores are much more distinctly marked ; there is only one distinct series of primary tubercles in each set of coronal plates above the ambitus ; below the ambitus there are indications of a second and, still more faintly, of a third series in the interambulacral areae; the anal covering-plates are for the most part large, and consequently few in number; the most striking in the specimen, 22*5 millims. in diameter, are five peripherally placed plates, which are separated from one another by small triangular plates, one for each. The test is much thinner in the fully grown than in the young specimens; the bare median spaces are more considerable in this than in any other species of the genus; and the tubercles are proportionally smaller; the actinal surface becomes a little swollen, so that the actinostome becomes somewhat depressed; the ridges connecting the not strongly developed auricles are low ; the madreporic is hardly larger than the other genital plates ; the anal opening is at or close to the centre of the anal area. 4. SALMACIS SULCATA, Ag. Salmacis sulcata, Agassiz & Desor, Catal. Rais., Ann. Sc. Nat. (3) vi. p. 359. Test rounded, or somewhat conical, closely covered with spines of a general green coloration, but becoming almost white towards |
