470 KEPTILIA, BATRACIIIA, AND MAMMALIA. 



to show that the work of separation has not been a sudden but 

 a very gradual i)ro(5ess, and due entirely to the general 

 subsidence of the hind. 



Chevremont, in the work I have already referred to, 

 estimates the rate of subsidence in this part of Europe at 

 15^ inclies per century during the last three thousand years. 

 Observations on the coast of Holland, Denmark and else- 

 where, show rates varying from as mucli as 36 inches per 

 century to the minimum (that of the last century) of 

 3 inches, but the rate acc^elerates as we go backward. Roman 

 roads of known age, now sul)merged to an ascertained depth, 

 on the North- Western coast of France, give 17^ inches 

 per century ; so that a fair average of its rate of subsidence 

 during say twenty thousand years can be estimated at 

 18 inches ; therefore to account for the depth of thirty feet of 

 water Avhich lies between Jersey and the mainland at low 

 tide, a period of two thousand years would be required, which 

 means a period of four thousand years, at least, since Jersey 

 was strictly continental, and accessible at all states of the tide. 



Let us now consider Guernsey. The Channel between 

 this island and Jersey is of fairly uniform depth from shore to 

 shore, namely, 210 feet at high tide, so calcidating at the 

 same rate of subsidence, fourteen thousand years must have 

 elapsed smce Guernsey Avas united to and formed part of the 

 mainland of France. 



This difference between the ages of the two islands 

 will account for Jersey having been the recipient of a greater 

 number of immigrants than its sister isle, and also allows time 

 for Guernsey to have evolved a field vole of its own as we 

 shall presently see has been the case. 



We are now in a position to consider that which is 

 the actual subject of this paj^er, the Reptilia, Batrachia and 

 Mammalia of the Islands. 



REPTILIA AND BATRACHIA. 



Of these two classes the Channel Islands possess eight 

 species, as follows : — 



Smooth Newt, Molge milgarls. 

 Palmated Newt, Molge palmata. 

 Common Frog, Raiui temjjoraria. 

 Common Toad, Byfo vulgaris. 

 Slow-worm, Anguis fragilis. 

 Wall Lizard, iMcerta mvralis. 

 Green Lizard, Tjacerta xnridh. 

 Common Snake, Coluber natrix. 



