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Show 1891-] MR. E. A. SMITH ON SHKLLS FROM ADEN. 395 15. TELLINA BALAUSTINA, Poli. ( = isseli, H. Ad.) " Quite undistinguishable from balaustina, Poli. I have examined large series of each without detecting any difference " (Cooke). On the contrary, H. Adams (P. Z. S. 1870, p. 790), who had ample or the same material before him, observes of his T. isseli:-" This species very much resembles T. balaustina, Linn., but the posterior side is somewhat more angulated, and the concentric striae, which are less numerous, are much stronger." These points of difference certainly do exist in the specimens from Suez, and 1 also notice that the form is rounder and the hinge-teeth proportionally stronger. I am therefore at present inclined to regard these two forms sufficiently specifically distinct. 16. GASTROCH^ENA DUBIA, Penn. (=riippellii, Desh.) This species undoubtedly occurs in the Red Sea (ruppellii), at Singapore (indistincta, Desh.), and the Philippines (lamellosa, Desh.). On comparing the types of the three Deshayesian species with specimens of G. dubia, I fail to discover any essential differences. 17. 1 PHOLAS DACTYLUS, L. (-erythrcea, Gray.) Of this species (erythrcea) Mr. Cooke writes-" It seems very doubtful whether the type shell at the Brit. Mus., from which this ' has been named, is anything more than dactylus, L." Now Gray correctly described his species as a Barnea, and this alone should have been sufficient to indicate its distinctness from P. dactylus. I have examined the types (two valves) of erythrcea and find that they are identical with B. manillensis of Philippi from the Philippine Islands. W e may therefore dismiss from our minds the notion that P. dactylus occurs in the Red Sea. A perusal of the above observations shows that three of Mr. Cooke's identifications I regard as entirely erroneous, namely: - 1. Pecten varius should be P. senatorius. 2. Spondylus gcederopus „ S. aculeatus. 3. Pholas dactylus „ Barnea manillensis. Four species, although closely resembling Mediterranean forms, I regard as sufficiently distinct for specific separation, viz.- 1. Emarginula elongata should be E. sp. nov. 2. Volvula acuminata „ V. angustata. 3. Modiolaria marmorata „ M. ccenobita. 4. Tellina balaustina „ T. isseli. 1 MacAndrew's one valve. |