1890.] MARINE MOLLUSCA OF ST. HELENA. 307 



features of this species. It probably attains larger dimensions than 

 those given above. The angle formed by the divergent dorsal 

 slopes is about 116 degrees. 



LiMEA SARsir, Loven. 



Limea sarsii, Loven, Index Moll. Scandin. p. 32. 



Lima sarsii, Jeffreys, Brit. Conch, vol. ii. p. 78, vol. v. p. 1G9, 

 pi. 2.5. fig. 1. 



Lima {Limatula) sarsii, Jeffreys, Proc. Zool. Soc. 18/9, p. .562. 



Limatuln crassa (Forbes), Sars, Moll. Reg. Arct. Norv. p. 26. 



Hab. North Sea ; Mediterranean ; Atlantic from west of Ireland 

 to Portugal. 



A number of odd valves were dredged in deep water by Capt. 

 Turton. The occurrence of this species so far south has not been 

 previously noted. 



OSTREA, Sp. 



A species of oyster occurs in very shallow pools on tlie east coast 

 of St. Helena, which, possibly, has not been previously described. 

 The same form is met with at Cape Verde Islands. It is thick, 

 solid, irregularly rounded, with the surface ridged and the maro;in 

 dentate and interlocking like O. folium and other species. Tiie 

 interior is dirty whitish, stained more or less with olive-brown or 

 yellowish olive, and the outer margin is finely wrinkle-striated. 



OsTREA CRISTA-GALLI, Linn. 



Bab. St. Helena, .50-60 fathoms {MelUss). 



I have not seen the specimens collected by Mr. Melliss and 

 identified by Jeffreys as belonging to this species, which is usually 

 regarded as an Indian-Ocean form. I think it probable that they 

 belong to the same species as those collected by Capt. Turton, 

 which I have not ventured to identify. Having strongly dentate 

 margins to the valves, they may have been mistaken by Jeffreys for 

 the Liunean species. 



APPENDIX. 



The following species were all taken at St. Helena upon floating 

 seaweed, but, as I have already shown \ are to be regarded as South- 

 African forms. 



I. GASTROPODA. 



Pleurotoma (Mangilia) atlantica. (Plate XXIV. fig. 11.) 

 Testa elongata,2^('tticle fusca, linea alha cincta ; anfractus 5, primus 

 maxinws, glohosus, nitidus, albidus, cceteri convexiiiscidi, plicis 

 longitudinalibus 10—12 instructi, liris striisque spiralibus ornati ; 

 anfr. ultimas elongatus, infra medium parum contractus ; aper- 

 tura angusta, longit. totius j^ adcequans ; columella alba ; lab- 

 rum vix incrassatitm, superne minime sinuatum,, 

 Longit. 6 millim., diam. max. 2^. 



This species is remarkable for the large size of the apex. The 



1 Pp. 247, 248. 



