MOLLUSCA.—HEDLEY. 
51 
1913, from 350-400 fathoms, ooze, in Commonwealth Bay, Adelie Land, in South Lat. 
66° 50' and East Long. 142° 6'. Four, January 21st, 1914, from 60 fathoms, bottom 
stones and red algae, off Drygalski Island, in South Lat. 65° 42' and East Long. 92° 10'. 
Trochaclis Antarctica Thiele. 
Trochaclis antarctica Thiele, Deutsch. Siidpol. Exped., xiii., 1912, p. 192, pi. xi., fig. 29. 
Two specimens, January 28th, 1914, from 240 fathoms, ooze, off the Shackleton 
Ice-shelf, in South Lat. 65° 20' and East Long. 95° 27'. 
Friginatica gen. nov. 
Examination of naticoid systematics induced Dr. W. H. Dali * to adopt Gray’s 
division by shelly and horny opercula. In the first case he selected Nerita vitellus 
Linne (which Hanley identified with N. rufa Born), as type of Natica of Scopoli, thus 
restricting that genus to shells with a concentrically furrowed operculum. Those 
which have a. single marginal sulcus on the operculum were referred to Cochlis Bolten, 
with N. vittata as type ; finally a group Cryptonatica, type N. clausa, was formed for 
species with a smooth operculum. 
Naticoids wearing a horny operculum were then grouped into Polinices with Nerita 
mammilla Linne as type, Euspira with Natica labellata as type and Cepatia with 
Natica cepacea as type. 
The Linnean Nerita mammilla is a compound, perhaps indistinguishable, species, 
given different values by various authors, but which Hanley and Watson recognise 
as Natica pyriformis Recluz = Mammillaria tumida Swainson. It appears from his 
illustration that Montfort regarded N. mammilla as a species like the West American 
N. uber Valenciennes. So that the oriental group usually considered as Polinices 
might, strictly in subdivision, be termed Mammillaria. 
There is an Antarctic naticoid group which cannot be received by any of the above, 
or by other known extralimital groups such as Cernina or Mammilla, not discussed 
by Dr. Dali. So far this amounts to about a dozen rather featureless species, all small, 
mostly uniform olive buff in colour, four whorls, a slightly raised spire, a caducous 
epidermis, comparatively thin, unsculptured, except for incremental striae, without 
umbilical funicle or a callus pad at the insertion of the right lip. Operculum corneous 
paucispiral. 
As type of Friginatica, I nominate Natica beddomei Johnston, well figured in the 
Gasteropoda of the “Challenger” under the later name of Natica effosa Watson, and, 
perhaps, identical with a Tertiary fossil Natica polita Ten. Woods. 
* Dali.—U.S. Geol. Survey Profess. Papers, 59, 1909, p. 85. 
