I2 o DISCOVERY REPORTS 



A third member of Falsilunatia appears to be Preston's Natica falklandica (19 13, p. 218) from Port 

 Stanley, Falkland Islands. It is thin and globose, relatively large and with more elevated spire-whorls 

 than in cither soluta or recognita, but its shape suggests Falsilunatia rather than Globisinum. Two 

 examples from the British Museum collection were examined (PI. X, fig. 61). The dimensions of these 

 specimens are respectively : height 17 mm., diameter 14-5 mm. ; and height 1475 mm., diameter 13 mm. 



Genus Sinuber n.g. 

 Type : Natica sculpta Martens 



The above new genus is provided for small Sinum-Hke species, the true relationship of which is 

 probably with Polinices rather than with Sinum. The shell is thin, white, with a very inconspicuous 

 epidermis, a transparent, almost colourless film; protoconch smooth and glossy, or with faint spiral 

 lines ; post-nuclear sculpture of deeply incised linear grooves ; umbilicus narrow and partly bridged, 

 not infilled, by a reflexed columellar callus ; columella almost vertical ; operculum paucispiral and horny. 



The radula is of a style common in the family and similar to that of Polinices and Amauropsis. Minor 

 differences are that the side cusps of the central tooth are relatively small, the laterals are deeply 

 sinused on their inner edge and bear three weak cusps, while the marginals have simple arcuately 

 pointed, not bifid cusps. It was shown by Troschel (1861, pi. 15, figs. 15, 16) and by Iredale (1924, 

 p. 256) that true Sinum has a broad central tooth with the two side cusps more prominent than the 

 central one. The Sinwn-like genera of Polinices affinity — i.e. Sigaretotrema Sacco, 1890 ( = Propesinum 

 Iredale 1924) and Eunaticina Fischer, 1885 — are not applicable either, for Iredale pointed out (loc. cit.) 

 that their tendency is for the central to become unicuspid. 



Sinuber sculpta (Martens) 



Natica sculpta Martens, 1878, p. 24. 



Natica sculpta Martens & Thiele, 1903, p. 65, pi. 4, fig. 1. 



Type locality. Kerguelen I. 



Form A. St. 1660. Ross Sea, 74 46-4' S, 178 23-4' E, 27 Jan. 1936, 351 m. 



Form B. St. WS 212. North of Falkland Is., 49° 22' S, 6o° 10' W, 30 May 1928, 242-249 m. 



St. WS 773. North of Falkland Is., 47 28' S, 60° 51' W, 31 Oct. 1931, 291-296 m. 



The type locality for sculpta is Kerguelen Island, and closely allied forms of it range southward to the 

 Ross Sea and westward to north of the Falklands, South Georgia and South Orkneys. 



Unfortunately, I do not have access to topotypic material, and Marten's description is rather lacking 

 in detail. His figure of the holotype, however (1903, pi. 4, fig. 1), and his measurements of the shell, 

 show that the South Orkney-South Georgia form is relatively wider and that the aperture is lower in 

 relation to the height of the shell. This form is described below as a new subspecies. 



Ross Sea examples (St. 1660) and those from north of the Falklands (St. WS 212 and WS 773) are 

 small, relatively narrow forms, the former openly umbilicate and the latter with the umbilicus almost 

 closed by the reflexed columellar callus. These two forms exhibit a difference in the number of spiral 

 grooves, but since I cannot make an accurate comparison with sculpta on this point, Ross Sea and 

 Falkland material must be tentatively referred to sculpta. 



Sinuber sculpta scotiana n.subsp., PI. V, fig. 10 

 Natica sculpta: Strebel, 1908, p. 62. 



This form differs from typical sculpta, as shown by reference to Marten's original description and 

 figure, in being relatively wider and with a lower aperture. The protoconch is faintly spirally striate, 

 and there are from sixteen to eighteen linear grooves on the first post-nuclear whorl, twenty on the 



