io 6 DISCOVERY REPORTS 



Type locality. St. 153. Off Cumberland Bay, South Georgia, 54 08' 30" S, 36 27' 30" W, 

 17 Jan. 1927, 106 m. 



St. 20. 14-6 miles N 41° E of Cape Saunders, South Georgia, 4 Mar. 1926, 200 m. 

 St. 42. Off mouth of Cumberland Bay, South Georgia, 1 Apr. 1926, 120-204 m - 

 St. 140. Stromness Harbour to Larsen Point, South Georgia, 23 Dec. 1926, 122-136 m. 

 St. 156. North of South Georgia 53 51' S, 36 21' 30" W, 20 Jan. 1927, 200-236 m. 

 St. 190. Bismarck Strait, Palmer Archipelago, 24 Mar. 1927, 315 m. 



Family LITTORINIDAE 



Study of the radulae of the southern Laevilitorinids indicates a greater complexity than is suggested 

 by their respective shells. Four genera have been in use — Laevilitorina, Pellilitorina, Haloconcha and 

 Macquariella. The first, second and fourth names were proposed for antarctic-subantarctic shells, but 

 the genotype of the third is northern and is based upon a little known and apparently quite local species 

 from the Aleutian Islands. 



Two main radula types are found in the southern shells: (a) with a broad, shallow-based central 

 tooth bearing five cusps, and (b) with a narrow, deep-based central tooth, variously cusped. Type 

 (a) is restricted to Pellilitorina and type (b) to the remainder. Type (b), however, subdivides into (bi) 

 with prominent, narrowly pointed cusps on both the central and lateral teeth, and (bz) with very broad 

 chisel-shaped cusps. Type (a) is found in relatively large, globose shells with only a narrow umbilical 

 perforation and an epidermis covered with hair-like processes. Type (bi) is found in Laevilitorina, 

 which is small, ovate-conical and imperforate, and in Macquariella, which is small, subglobose and 

 narrowly umbilicate. Type (bz) is found in Lacuna antarctica Martens, 1885, which Thiele (19 12) 

 referred to Haloconcha; Pellilitorina bransfieldensis Preston, 1916, which is almost identical with 

 antarctica; Pellilitorina bennetti Preston, 191 6; and Laevilitorina coriacea Melvill & Standen, 1907. 



The type (62) group, however, present three distinct shell types: (1) antarctica and bransfieldensis, 

 which have a broad, depressed, heliciform shell with a wide umbilicus ; (2) bennetti, which is globose 

 and narrowly umbilicated ; and (3) coriacea, which is ovate-conical and imperforate and of identical 

 shape to Laevilitorina. 



Several new names are required to arrange these shells in a natural grouping and they are diagnosed 

 as follows: 



Genus Laevilitorina Pfeffer, 1886 (Type : Hydrobia caliginosa Gould). Tierra del Fuego to Macquarie 

 Island. Shell small, ovate conical, imperforate or almost so, epidermis smooth. Radula (Fig. I, 26) 

 with a narrow central tooth, central and laterals with several prominent, narrowly pointed cusps, 

 marginals fan-shaped and multidenticulate. Includes pygmaea, venusta, granum and umbilicata Pfeffer, 

 1886, South Georgia, bennetti and latior Preston, 191 2, Falklands and probably claviformis Preston. 



Subgenus Corneolitorina n.subg. (of Laevilitorina) (Type: L. coriacea, Melvill & Standen), South 

 Orkneys. Shell small, ovate-conical, imperforate, as in Laevilitorina, but scarcely any shell substance 

 apart from a thick leathery epidermis. Radula (Fig. I, 27) with a narrow central tooth, central and 

 laterals with the main cusps blunt, chisel-shaped, marginals narrow with about seven denticles. 

 Pelseneer's L. elongata (1903, pi. 5, fig. 58) from Two Hummocks Islands may belong here also. 



Genus Macquariella Finlay, 1926 (Type Paludestrina hamiltoni Smith) Macquarie Island. Shell 

 small, subglobose and narrowly umbilicated. Radula (Fig. I, 31) with an extremely narrow central 

 tooth bearing only one long, sharp cusp, first lateral with a long central cusp and two shorter cusps, 

 second lateral with three long cusps, marginals multidentate. Includes Macquariella aucklandica 

 Powell, 1933, from Auckland, Chatham and Stewart Islands, New Zealand. 



Genus Laevilacunaria n.g. (Type: Pellilotorina bransfieldensis Preston), South Shetlands. Shell 



