1891.] MR. E. A. SMITH ON SHELLS FROM ADEN. 395 



15. Tellina balaustina, Poli. 

 ( = isseli, H. Ad.) 



" Quite uudistinguishable 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 proportionallv stronger. I am 

 therefore at present inclined to regard these two forms sufficiently 

 specifically distinct. 



16. Gastroch^na dubia, Penn. 

 (^=ruppellii, 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. ? Pholas dactylus, L. 



(^ = erythrcsa, Gray.) 



Of this species (eri/thrtea) 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 tiie types (two valves) of erythrcea and find that they 

 are identical with B. manillensis of Philippi from the Philippine 

 Islands. We 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 „ F. angustata. 



3. Modiolaria marmorata ,, M. ccenobita. 



4. Tellina balaustina „ T. isseli. 



* MacAndrew's one valve. 



