THE FALKLAND AREA 297 



elsewhere by any other species of the genus. Its dominance in the Falklands is one more 

 of those mysterious problems of distribution which need solution. 



Elphidiiim {Polystomella) lessonii (d'Orbigny), which is a handsome species often com- 

 mon in the Falkland material, appears to be almost (if not wholly) confined to the area. 



The species Herouallenia (Discorbis) kempii, which is one of the largest and certainly the 

 handsomest species in the genus, appears to be confined to the Falklands, where it is 

 found only in the southern area between the Burdwood Bank and a line running from 

 the Magellan Straits round the southern shores of the islands. Its nearest relatives are 

 almost wholly of Pacific habitat, and it appears unquestionable that this species is an 

 immigrant of comparatively recent Pacific origin which has not yet had time to spread 

 over the more distant parts of the Falkland area. 



There are several other species which can be assumed to have migrated from the 

 Pacific to the Falkland area, but in most cases there can be no definite proof owing to the 

 paucity of records. We list several species which d'Orbigny recorded from the west 

 coast of South America but not from the Falklands. But it would be very dangerous to 

 regard these as immigrants on such evidence alone, in view of the notorious tendency of 

 d'Orbigny to overlook, or disregard, species with which it is certain that he was familiar. 

 The mere fact that he did not identify and name the dominant Uvigerhia angulosa, one 

 of the two commonest and most widely distributed of the Falkland species, is sufficient to 

 prevent his records from being taken too seriously as evidence of extension of locality. 



The species in regard to which there is the best and most definite evidence of extension 

 of habitat is Rotalia clathrata, Brady. This is a common and typical species in Australian 

 waters and is also found in the Miocene of Victoria. Between that area and the west 

 coast of Patagonia, where it was found among the islands by the Challenger Expedition, 

 there are no records of its occurrence. Now we record it from the Falklands at thirteen 

 stations, nearly all of which are south of a line running from Magellan Straits round the 

 southern shore of the islands. The finest examples, which are quite equal to the New 

 Zealand types, came from the three stations WS 86, 87, 88, which lie stretched across 

 the southern entrance to the Falkland area, between the extremity of the Continent and 

 the Burdwood Bank, while at WS 89, 90, further north and nearer the Magellan Straits, 

 the specimens are small and starved. The west of Patagonia specimens are stated by 

 Brady to be smaller and weaker than the New Zealand type. It seems certain in this 

 case that the species has reached the Falklands via the Horn and not by way of the 

 Magellan Straits and that it is diminishing in size as it passes northwards into less 

 favourable surroundings. If it had travelled via the Straits, its distribution would 

 presumably have extended to the north of them as well as to the south. 



There is of course an alternative possibility that the New Zealand, Patagonian and 

 Falkland colonies are separate survivals from a Miocene sea in which the species occurred 

 universally between these areas. But we have no geological information bearing on such 

 a speculation beyond the fact that numerous fossil Foraminifera were found in the bottom 

 deposits at several stations, particularly at station WS 87 on the Burdwood Bank, where 

 they were found in such numbers as to suggest a submarine outcrop of some fossiliferous 



