1901. J MOLLUSKS FBOM THE PEESIAN GULF. 359 



Natica steongtla Melv. 



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

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

 the Andamans {Booley). 



Natica traillii Eeeve. 



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

 Natioa (Eunatica) tranquilla, sp. n. (Plate XXII. fig. 5.) 

 N. testa glohosa, nitida, solidiusciday apud umbilicum alho-ccdlosa, 

 umhilico angusto, profunde perforata; anfractihus, apicaliincluso, 

 sex, perlcevibus, ventricosidis, apud suturas paidlidmn eoscavatis, 

 pallide albo-cinereis, obscurissime castaneo-vittatis vel fasciatis, 

 ultimo anfractu rapide accrescente, omnino Icevi, fascia centrali 

 castanea circa regionem umbilicareni pulchre et regidariter 

 sagittifera ; apertura ovata, castaneo-tincta ; labro, prcecipue 

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

 centraliter Icevissimo, fortiter marginato, nucleo centrali. 

 Alt. 11, cliam. 13 mm. 

 Hab. Gulf of Oman, Maskat. 10 fathoms. 

 This Natica differs from all forms of the protean and widely 

 distributed N. marocJiiensis 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 marocJiiensis, 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 (Nevbrita) didyma Bolten (JSf. ampla Phil.). 

 M.C. Generally distributed. 



I. Karachi. Bombay {Abercrombie), and southwards (Lt.-Ool. 

 H. D. Olivier). 



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



Natioa (Mamma) albumen L. 



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

 pellucid variety. 



Natica (Mamma) cumingiana Eecluz. 

 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 Eecluz. 



Natica (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 above localities include records for N. pgriformis Recluz, 

 which seems hardly even a variety. 



I. Bassein. Bombay ; common southwards (Lt.-Ool. H. D. Olivier). 



