FORAMINIFERA— HERON-ALLEN AND EARLAND. 33 



Arctic and adjacent seas. They are Reophax arctica, Brady, known only from tlie 

 Arctic, and by a few pauperate specimens from Delos (Sidebottom), Hippocrepina 

 indivisa, Parker, known from the Gulf of St. Lawrence, the Arctic seas, and in a 

 starved form from the Moray Firth ; Polystomella arctica, P. & J., perhaps the 

 most typical and abundant of all Arctic species, a large, strong species which 

 cannot be overlooked and with a Southern limit about the Moray Firth. 



None of these three forms have esyer been recorded from the Southern area, 

 and but for the occurrence of a single specimen (broken) of Hippocrepina indivisa 

 in our own records we should regard their complete absence as more striking than 

 the occurrence of a multitude of other species which have a more or less universal 

 distribution. 



It is more difficult to select sunilar forms from the Southern area, but there 

 are two characteristic Antarctic forms which may be considered, viz. : 



(1) Articulina funalis, Brady, abundant in the farthest South gatheruigs. 

 This has been recorded also from shallow water in the tropics, but never, so far 

 as we know, in Northern Seas. 



(2) Ehrenbergina hystrix, Brady, represented abundantly in the Antarctic by 

 our variety glabra, and otherwise known only from deep water in the Pacific. 



Practically the only species (so called) which could be invoked as evidence 

 of bipolarity is Globigerina pacliyderma (Ehbg.). This curiously thick- walled and 

 verv characteristic form is the typical Globigerina of Arctic deposits. Pace Sir 

 John Murray* it is a purely benthic form, its very structure is opposed, in our 

 opinion, to any idea of its existence in the pelagic state. Abundant in the Arctic 

 oozes, it becomes rarer in the North Atlantic, and, save for perhaps an occasional 

 doubtful specknen, such as the records from the Pacific (B. 1884, F.C., p. 777), 

 reaches its southern limit m the Faroe Channel. It does not form a constituent of 

 the bottom oozes of temperate and warm seas, as might be expected if it were either 



(1) Pelagic, as stated by Murray, we believe in error. 



(2) Benthic, but generally distributed. 



Yet Globigerina pacliyderma (Ehbg.), occurs in the Antarctic as the typical 

 Globigerina at all depths. 



As we have stated elsewhere m our notes on the two species, the explana- 

 tion of the occurrence of this Arctic form in Antarctic oozes, and its absence in 

 intermediate deposits, lies in the fact that it is not a true species, but a local 

 variation of Globigerina dutertrei, d'Orb., induced by conditions of temperature. 

 The same gradual transition of the one type into the other which we have 

 described in the Antarctic could be traced in the Arctic and temperate seas, and 

 although the records of G. dutertrei are smgularly few (probably because it is 



* J. Murray, " The Ocean" (London, n.ci.) 1913, p. 165 and "Pelagic Foraminifera " 1897, Nat. 

 Science, vol. xi, pp. 17-27. 



