434 TIIE VOYAGE OF H.M.S. CHALLENGER. 



Nerita marochicnsis, Gmelin, Syst. Nat., p. 3673, No. 15 ; — Natica marochicnsis, Lamarck, Anim. s. 

 vert., vol. vi. (2), p. 203, and (ed. Desh.) vol. viii. p. 642, sp. 25, (Natica unifasciata, Lam., 

 Delessert, Recueil, pi. xxxii. fig. 13, is a synonym, see Deshayes' note on p. 625, loc. cit. supra) ; — Nerita 

 marochicnsis, Wood, Ind. Test., p. 178, pi. xxxv. fig. 14; — Natica maroccana, Philippi, Conch. Cab. 

 (ed. Ktister), p. 78, sp. 18, pi. iii. figs. 10-13, 25, 26, pi. xii. figs. 1—5 ; — Natica marochicnsis, Reeve, 

 Conch. Icon., vol. ix. pi. xiii. fig. 52 ; — Natica marochicnsis, Sowerby, Thes. Conch., pts. 39, 40, p. 82, 

 sp. 38, pi. cccclxi. (viii. Gen.) figs. 108, 109, and pi. cccclxii. (ix. Gen.), fig. 151 ; and v. Martens, Moll. 

 Mauritius, &c, p. 276. A full but not quite satisfactory statement by Koch regarding the synonymy 

 of the species will be found in Menke's Zeitschrift f. Malak., 1845, p. 151. A note, too, on the 

 subject by Carpenter will be found in the Proc. Zool. Soc. Lond., 1863, p. 357, which, taken in 

 conjunction with what he had said in Proc. Zool. Soc. Lond., 1856, p. 227, would have led one to 

 expect a separation of the Pacific and Atlantic forms at least. 



The operculum of this species does not seem to have been described. It is in form gibbously oval 

 — calcareous, with a thin, brownish-yellow membrane covering the interior face — pretty strong, 

 being thickened and hunchy in the middle : the coils of the spire, which are shown on the interior 

 face, are on the exterior face thickened with a largish diffused brownish pad : toward the upper pillar 

 border the whole exterior face is somewhat undulating, and thins off to a blunt, narrow, but squarish 

 and longitudinally scored edge on the outer border, where it is edged by a single narrow very slightly 

 raised rounded rim, on the inner side of which is a shallow ill-defined furrow. 



In Natica maroccana, Chem. (dillwynii, Payr), the calcareous operculum is discoidal, being thin and 

 almost quite flat on both faces. Only on the front of the spire there is a slight, smallish, irregularly 

 pear-shaped, darkish coloured thickening ; round the outer margin is a slightly raised narrowish 

 border, divided longitudinally into two ridges by a deep sharp-cut narrow cleft, towards which the 

 surface of both the ridges is bevelled up. The inner and slightly broader ridge is parted from the 

 flat part of the surface by a strongish square-cut furrow, which is rather broader than the ridge. 

 The outer ridge is bordered outside by a very narrow flat shelf. 



I have described these opercula thus minutely because the operculum in Natica is a very con- 

 stant feature, and the difference between the two species in question, though not more certainly 

 established, is at least more strikingly shown in their respective opercula than it is elsewhere. 



6. Natica seychellium, Watson. 



Natica mahesense, Recluz MS. 



,, maheense, Reeve, Conch. Icon., vol. ix. pi. xiv. fig. 58. 



„ „ Brazier, " Chevert" Exped. Mar. Shells, Proc. Linn. Soc. New South Wales, 1877, 



vol. i. p. 235, No. 45. 

 „ maheensis, Sowerby, Thes. Conch., pts. 39, 40, p. 81, sp. 36, pi. cccclvii. (iv. Gen.) fig. 40. 



Station 212. January 30, 1875. Lat. 6° 54' N., long. 122° 18' E. Off Malauipa, 

 Philippines. 10 to 20 fathoms. Sand. 



Habitat. — Mahe" in the Seychelles (Reeve and British Museum) ; Torres Strait, 30 

 fathoms (Brazier). 



