68 DISCOVERY REPORTS 



These genera are stenothermic, for in the New Zealand Subantarctie groups, Campbell and Auckland 

 Islands, the common limpets are of the subtropical genus Cellana which occurs to the entire exclusion 

 of Patinigera over the rest of the New Zealand area to the north. 



■S" 



Family Fissurellidae 



The large Fissurellid subgenus Balboaina is restricted to the Magellan Province. The species 

 Puncturella cofiica, which is found in most southern high latitudes, is distinguished only with difficulty 

 from the boreal genotype. It is a good example of a ' bipolar ' genus which ranges deep over the warm 

 zones. The route of migration to the south or vice versa could be either the eastern or western American 

 coastlines, or both. Parmaphorella occurs in the Magellan Province and extends via the Atlantic- 

 Indian Ocean cross-ridge to South Africa. The related genus Tugalia is found in warm water in the 

 East Indian-Australian-New Zealand regions. 



Family Trochidae 



The Trochoids form a conspicuous element in the Antarctic- Subantarctie region (see Fig. C). 



A. Calliostoma group. True Calliostoma does not extend farther south than the Magellan Province, 

 but the following genera are specialized Antarctic-Subantarctic derivatives of Calliostoma : 



(i) Photinula. Magellan, 0-202 m. 



(2) Photinastoma. Magellan, 0-1 15 m. 



(3) Venustatrocfws n.g. South Georgia only, 120-204 m. 



(4) Falsimargarita n.g. Falkland Islands, South Shetland Islands and off Oates Land, 69 43' S, 

 163 24' E, 250-468 m. 



B. Margarella group. This is a wide-ranging, high-latitude southern genus related to the boreal 

 Margarita. Many of its members are directly herbivorous, and its circum-subantarctic range no doubt 

 has been assisted by the direct agency of the West Wind Drift. The genus is common in the Magellan 

 Province, South Georgia to Graham Land, eastward along the Antarctic Continental Shelf to the Ross 

 Sea and via the Atlantic-Indian Ocean cross-ridge to Marion Island, the Crozets, Kerguelen, Macquarie 

 Island, the subantarctie islands of New Zealand, and the southern and eastern coastline of the South 

 Island of New Zealand to about 42 S. The New Zealand members are littoral species mostly restricted 

 to the holdfasts of the giant kelp D'Urvillea. 



The subgenus Promargarita is restricted to South Georgia, and the somewhat related Sabmargarita 

 ranges from South Georgia to Kerguelen and the Davis Sea. 



Other Margarita-Yike genera are the elaborately sculptured Antimargarita n.g., circum-antarctic in 

 deep water (130-400 fathoms) and Tropidomarga n.g., South Georgia and Clarence Island, 160-342 m. 



Solariella occurs in deep water from the Falklands to Heard Island and Kerguelen. The genotype is 

 from the English Pliocene, but the genus is well represented in north-west America, the North Atlantic 

 and the Indian Ocean. 



From the above it can be assumed that this considerable southern high-latitude radiation of Trochoids 

 originated from the American Quadrant. 



Family Littorinidae 



The periwinkles are represented by the wide-ranging, mainly subantarctie genus Laevilitorina, 

 several specialized genera from the higher latitudes of the Scotia Arc, and Pellilitorina, which has been 

 recorded from the Burdwood Bank, South Georgia, South Orkneys, South Shetlands, Bouvet Island, 

 Kerguelen and Cape Adare (Antarctica). A South Australian species, globula Angas, 1880, has been 

 referred to Pellilitorina, which it certainly resembles, but this claim requires confirmation. 



