CH. Ill] ANTARCTIC CRUSTACEA. 161 



appears that not more than 20 are found on the west 

 coast of North America." The proportion, in fact, instead 

 of being three-fourths is one-twentieth. It will be re- 

 membered also, in estimating the significance of these 

 facts, that the coasts of Japan enjoy a climate and tempe- 

 rature that is not widely different from that which is en- 

 joyed by the coasts of the part of America brought into 

 comparison. 



We may take as another example the Isopod Crusta- 

 ceans of the antarctic region which have been investi- 

 gated by the " Challenger," " Gazelle," and recently by the 

 German Polar expedition, the results of all these expedi- 

 tions having been carefully reported upon by Dr Pfeffer. 

 He enumerates 55 marine species of which only five have 

 at all an extensive range, and two of these, which are 

 stated to inhabit at once the shores of Patagonia and of 

 Rio Janeiro, are queried. As to a more northward ex- 

 tension there are no species which show any signs of it. 

 The genera enumerated are in all 27 ; and out of these 

 11 are limited to the southern ocean in the antarctic area. 



So much then for the first series of facts, which is that 

 the wide past distribution of marine animals contrasts 

 with the present limited distribution of the same, even 

 along areas which have very similar climatal conditions. 



Many geologists, including Mr Mellard Reade 1 , have 

 pointed out the extreme similarity between the con- 

 temporaneous or supposed contemporaneous rocks in 

 different parts of the world. When we "consider the 

 rocks." says the last-mentioned observer, " constituting the 



1 Natural Science, 1894. 

 B. Z 11 



