1S75.] 83 



XI.— Descriptions of new Marine Mollusca from the Indian Ocean. 

 By G-. and H. Nevill. 



(Received July 15th ; — Eead August 4th, 1875.) 

 (With Plates VII and VIII.) 

 The types of the new species of shells described in this paper mostly 

 belong to the family Pleurotomidce, and are all in the collection of the 

 Indian Museum. 



Mtjeex (Ocinebea) gibba, Pse. 

 Latirus giblus, Pease, Am . J. Conch., 1867, (Sandwich I.) 

 Hurex Crosseana, Lien., J. de Conch., 1874, (Mauritius). 



We have found this shell at Ceylon, the Seychelle, and Andaman 

 Islands ; it is nowhere a common shell. 



Mtjees (Ocestebba) eiscellttm, Ch. var. 



Chemn., Conch. Cat)., fig. 1524-5, (Tulo Condor). 



M. Zie'nardi, Crosse, J. de Conch., 1868, (Mauritius). 



We have found both the type form and the var. Lienardi at Mauri- 

 tius, also at Ceylon and Aden the above var. only ; a large series of speci- 

 mens in all stages of growth show that the two forms cannot be retained 

 as distinct species. — The very common Sistrum undatum (Ch.,fig. 1851-2, 

 Tranquebar) must not be confused with the above, as well pointed out 

 by Chemnitz in his original description, as also by v. Martens (Vorderasiat. 

 Conch., p. 95) ; we have found the typical form of S. undatum, with 

 whitish aperture, at Ceylon, Mauritius, and Natal; var. Indica, nobis, (de 

 Blainv. pi. X, fig. 8) at Ceylon, Mauritius, Singapore, Bombay, Anda- 

 mans, Penang, Arakan, Bourbon, and Seychelles ; var. subturrita (de Blainv. 

 pi. X, fig. 12) at Mauritius only, where it is rather scarce ; the Museum 

 also possesses specimens of var. margariticola, Brod. (Conch. Icon., fig. 28) 

 from the N. Coast of Australia : this form differs from var. Indica by the 

 fewer, more nodulous ribs, becoming more rapidly obsolete, by its stouter 

 and thicker growth, by the more regular transverse sculpture, and by its 

 more sombre colouration. 



Contjs Cetlonensis, Brug. 

 As already surmised by v. Martens (Don. Bism., p. 32), Pease is wrong 

 (Am. J. Conch., 1867, p. 126) in uniting Conus Ceylonensis, Brug. with 

 Conus pusillus, Ch. (Conch. Icon. fig. 154) ; both are abundant species 

 at low water on the reefs at Ceylon and the Andamans ; the latter species 

 we have also found at Mauritius and the Seychelle Islands. Not only, how- 



