624 ZOOLOGY sect. 



union, moreover, it was largely submerged, so as to leave no trace 

 of its Pliocene fauna. Thus, the British animals are all migrants 

 from Europe, isolated by the post-glacial separation from Europe, 

 and the absence of certain European forms is due to the fact 

 that the separation took place too early to allow of complete 

 migration. 



New Zealand, on the other hand, instead of being separated from 

 the nearest continent by 21 miles of shallow sea, is divided from 

 Australia by 1,000 miles of ocean — the Tasman Sea — varying 

 from 2,000 to 2,600 fathoms (12,000-15,600 feet) in depth. It is 

 almost certain that there was never any direct connection between 



Fig. 1240.— Map showing depths of sea around Australia and New Zealand. The light 

 tint indicates a depth of less than 1,000 fathoms ; the dark tint indicates a depth 

 of more than 1,000 fathoms. (From Wallace.) 



the two countries, and the only indication of even an indirect con- 

 nection is afforded by the existence of an area of comparatively 

 shallow sea — i.e., under 1,000 fathoms — stretching between the 

 North Island of New Zealand on the one hand, and Northern 

 Australia and New Guinea on the other (Fig, 1240). It would 

 take therefore, an upheaval of over 6,000 feet to join the two 

 countries, and it may be taken as certain that if there ever was a 

 direct connection, either by continuous land or by a chain of islands, 

 such connection could not have been later than the early part of 

 the Mesozoic era. 



It must also be noted that while the British fauna is related 



