SYSTEMATIC 117 



Type locality. Hut Point, 'Discovery' Winter Quarters, McMurdo Sound. 

 St. 1660. Ross Sea, 74 46-4' S, 178° 23-4' E, 27 Jan. 1936, 351 m. (one juvenile, 12 x 1 1-5 mm.). 



Range. McMurdo Sound, 140-300 fathoms; off Mertz Glacier Tongue, Adelie Land, 288 fathoms; 

 Ross Sea. 



Dentition. Fig. J, 43, p. 192 (Eales, 1923, loc. cit. p. 21, fig. 21). 



This species is very closely allied to aureolutea, but has a more deeply impressed suture and the 

 spiral sculpture is more pronounced. The operculum is horny. 



The solitary ' Discovery' example has a slightly lower spire than topotypic examples from McMurdo 

 Sound, 250 fathoms. 



Amauropsis georgianus Strebel 



Natica georgiana Strebel, 1908, p. 62, pi. 5, fig. 65 a, b. 



Type locality. South Georgia, 64-74 m - 

 St. 45. 27 miles S 85° E of Jason Lt., South Georgia, 238-270 m. 



I have not seen type material, but suspect that this may be merely a form of anderssoni. 



Subgenus Kerguelenatica n.subg. 

 Type: Natica grisea Martens, 1878 



At least subgeneric status is warranted for grisea, for it has an operculum which is formed of both 

 horny and calcareous materials. It is admirably described by Watson (1886, p. 432) as follows: ' It has 

 a thinnish calcareous layer over a pretty strong horny interior, which projects uncovered round the 

 entire edge, but this uncovered edge is narrowest on the inner side, i.e. near the pillar of the shell or 

 spire of the operculum. Here the exterior flat surface of the calcareous layer is thickened by a thin, 

 dirty grey, spreadout spot of limy substance. Beyond this spot the surface of the calcareous layer is 

 strongly scored with radiating lines. Its inner surface can be seen through the horny layer to be 

 sharply and delicately striate spirally.' Like the Amauropsis series the shell lacks a funicular callus and 

 has a thick yellowish brown epidermis. 



As already explained under Amauropsis, the species grisea cannot be covered by Friginatica as Hedley 

 intended, for the south-eastern Australian genotype, beddomei, apparently lacks epidermis, and according 

 to Cotton (193 1, p. 20) the operculum is horny. 



Unfortunately, in describing the Macquarie Island Friginatica pisum Hedley (191 6) made no reference 

 to the operculum, but Tomlin (1948), p. 228, remarked that it is ' dark coloured and horny.' The species 

 may be located provisionally in Amauropsis. I favour reinstating Marwick's Sidconacca (1924, p. 556), 

 type : S. vaughani Marwick, Lower Miocene, New Zealand, in preference to Friginatica which becomes 

 restricted to its Recent south-eastern Australian genotype. Sulconacca has the umbilical area margined 

 by a strong spiral ridge. 



The presumed occurrence of Amauropsis in both the Arctic and Antarctic regions may seem un- 

 natural and certainly brings up once more the question of bipolarity. 



Amauropsis is a high-latitude stenothermic mollusc related to Polinices, which is widely distributed in 

 warmer seas. Polinices is of considerable antiquity (common in the Tertiary of most regions), and it is 

 likely that Amauropsis also had sufficient time and opportunity during the colder periods of the 

 Pleistocene to accomplish bipolar distribution. The new subgenus Kerguelenatica is considered to be 

 a local product from Amauropsis originating in the Kerguelenian Province. From consideration of 

 time Sulconacca is probably not related nor is Friginatica in its restricted usage. 



