On the Lysianassa magellanica etc. 



5 



been a glacial-period which has connected the faunas of these now widely 

 separated tracts. 



Between the faunas and floras of the Arctic and Antarctic regions, it 

 is generally known that there prevails, a certain correspondence, so that one 

 not unfrequently meets in both with representatives of the same family & 

 genus, but it is extremely rare to find in both representatives of the same 

 species, and the instances hitherto recorded appear most generally the result 

 of confounding different species. As regards animalia vertebrata we with 

 certainty know of only one species J ) common to both zones, and among land- 

 animals not one common distinguishing genus occurs. Among these the ge- 

 nera which are represented in both zones are in general of a cosmopolitical 

 nature. It is among the inhabitants of the seas that we find examples of 

 an agreement between the zones. Within the class of Mammalia such an 

 example occurs among the Phocidae in the genus Cystophora Nilsson, al- 

 though that genus includes a species from the West-Indian seas. From 

 the Arctic Ocean we have the species Cystophora cristata. (Erxl.) and from 

 the Antarctic Cystophora leonina (Lin.) or prohoscidea (Desm.) Nils., which 

 however has by J. E. Gray, though apparently without sufficient reason, 

 been considered a separate genus, Morunga. Within the same class we 

 have among the Cetacea the genus Delphinapterus or Beluga with two spe- 

 cies: D. leucas (Pallas) from the Arctic and I). Kingii (J. E. Gray) from 

 the Antarctic Ocean. 



The feathered vertebrata or birds which on their swift wings move 

 to distant tracts with great rapidity, not unfrequently afford, as might be 

 expected, examples of a very extensive geographical dispersion, and we 

 find in the Arctic zone many species common to Europe, Asia and North 

 America, which have been termed circumpolars , and others that are extended 

 from the polar circles to the Equatorial regions. Nevertheless perhaps not 



') Otus brachyotus has been mentioned by d'Orbigny as found at the Strait 

 of Magellan, but Gould considers it to be a different species and calls it Otus Gala- 

 pagomsis as also occurring in the neighbourhood of the Galapagos Isles (Voyage of 

 Beagle 1, but Sciilegel has since (Museum des Pays-Bas) quoted that form, marking 

 it however with a note of interrogation, under the name of Otus brachyotus. D'Or- 

 bigny has also taken up the Procdlaria gladalis as found in the Strait of Magellan, 

 but it has since been found to be of a distinct species, and has even been referred 

 to another genus, Thalassoica ReiCHENBACH, Tlialass. glaeialoides Reich. Bonaj>. D'Or- 

 bigny has further stated that Hirundo rustica, urbica and riparia as well as Totamis 

 fuscus are found in Patagonia, hut in this also he appears to have confounded dif- 

 ferent species. 



