10 INDEX FAUN^, NOV.E ZEALANDI&. 



spinosus, and Acanthias vulgaris. There are also a few Crustacea 

 and mollusca, such as Saxicava artica and Mytilus edulis, as well 

 as many polyzoa, of which the southern forms are considered to 

 be identical with those inhabiting the northern seas. 



But bipolar species are not exclusively marine. Retropinna. 

 belongs to the northern Salmontdce. The fresh-water spider 

 Cambridgea is almost identical with Argyroneta of Europe. 

 Lycosa piratica is also found in New Zealand under conditions 

 which make its importation by man very improbable. Brachaspis, 

 a flightless grasshopper, is related to Pezotettix ; and among the 

 beetles there are Cillenum, Trogoph/czus, Pycnomerus, Philothermus, 

 Dendrophagus, Te/matophilus, Betarmon, and others. 



Attempts have been made to account for the Scandinavian 

 element in the New Zealand flora by the supposition of a general 

 glacial epoch all over the world, during which the Arctic plants 

 passed from mountain top to mountain top through the tropics. 

 But it is now considered very doubtful if there ever was a general 

 glacial epoch, and even if there was one it could not explain the 

 occurrence in New Zealand of northern beetles, grasshoppers, and 

 spiders. It seems more probable that these bipolar forms at 

 some former time inhabited the tropics; but that owing to 

 variation and change being more rapid in warm than in cold 

 climates a statement not yet proved the older forms were 

 exterminated in the warmer regions, being replaced by their more 

 highly developed descendants, the present tropical fauna. 



The Atlantic Island Element. Lastly we see in some of the 

 beetles a remarkable connection between the islands of the 

 Atlantic and those of the Pacific, in which New Zealand shares. 

 This is shown by the genera Rhynchogonns, Acalles, Pentarthrum, 

 and Aglycyderes, all belonging to the Rhynchoplwra ; and Xenoscelis, 

 belonging to the Nitulida. It is most probable that these, also, 

 are relics of a former more universal distribution ; the islands 

 serving as harbours of refuge, while their continental relations 

 were exterminated. 



Of Uncertain Origin. The distribution of Peripatus is 

 difficult to explain, as it is found in the West Indies, Central 

 and South America, and South Africa, as well as in the Malay 

 Peninsula, New Britain, Australia, and New Zealand. It is 

 supposed to have originated in Central America, and to have 

 migrated from thence. If this is correct, it could not have 

 reached Chili before the Miocene period, for before that time 



