1901.] MOLLUSKS FROM THE PERSIAN GULF. 359 



Natica strongtla Melv. 



P.G. Shaikh Shuaib I. Kais (or Gais) Island. Hindarabi I. 

 Usually about 7-10 fathoms, on coral-sand bottom. Extends to 

 the Andainans (Booley). 



Natica traillii Eeeve. 



P.G. Gulf of Oman : Maskat, 15 fathoms. I. Karachi. 



Xatica (Eunatica) tranqcilla, sp. n. (Plate XXII. fig. 5.) 



N. testa globosa, nitida, solidiuscula y apud umbilicum albo-ccdlosa, 

 umbilico angusto, profundi perforato; (infractions, apicali incluso, 

 sex, perlcevibus, ventricosulis, a/pud suturas paxdlulum excavatis, 

 pallide albo-cinereis, obscurissime castaneo-vittatM >'el fasciatis, 

 ultimo anfractu rapide accrescente, oninino Icevi, fascia centrali 

 castanea circa regionem umbilicarem pulchre et regulariter 

 mgittifera ; apertura ovata, castaneo-tincta ; labro, pra>dpue 

 circa columellam, albo-calloso, nitido ; operculo albo, nitido, 

 centra-liter Icevissimo, fortiter marginato, nucleo centrali. 



Alt. 11, diam. 13 mm. 



Hab. Gulf uf Oman, Maskat. 10 fathoms. 



This Natica differs from all forms of the protean and widely 

 distributed N. marochiensis Gmel., with "which Tryon (Man. Conch, 

 vol. viii. p. 22) has merged nearly thirty so-called species, in its 

 perfectly smooth surface at the sutures, nor trace of any plications 

 being visible. Likewise the operculum is peculiar ; the strong 

 marginal ridge not being present in marochiensis, which is com- 

 pletely smooth throughout. We may add, that we consider the 

 operculum an important factor in the differentiation of, at all events, 

 the typical section of this difficult genus, so many species of which 

 are very nearly allied. 



Natica (Xetbrita) didyma Bolten (N. ampla Phil.). 

 M.C. Generally distributed. 



I. Karachi. Bombav (Abercrombie), and southwards (Lt.-Col. 

 H. D. Olivier). 



Usually found from low tide to 3 fathoms, mud and hard sand. 



Natica (Mamma) albumen L. 



1. Lat. 18° 58' N., long. 71° 45' E. 40 fathoms. A semi- 

 pellucid variety. 



Natica (Mamma) cumingiana Reeluz. 

 P.G. Henjam Island. 10 fathoms, sandy mud. 

 Mr. Townsend notes as a curious fact that his single specimen, 

 though alive when dredged, was destitute of an operculum. 

 Tryon unites this with N. powisiana Rccluz. 



Xatica (Mamma) mamilla L. 

 P.G. Gulf of Oman,M askat. 



M.C. Occurs generally from low-tide mark to 10 fathoms, on 

 muddy sand. 



The abov • localities include records for X. pgriformis Rccluz, 

 which seems hardly BY8D a variety. 



I. Bassein. Bombay; common southwards Li .-< V. II . I). Olivier). 



