268 



CHANNEL ISLANDS' FAUNA. 



of which, from the rocks of Porsal to the mouth 

 of the Avranches river, runs due east for one 

 hundred and sixty miles. This part of France is of 

 old date in the earth's history. The chain of hills 

 of the " Cotes du Nord," and those of the Boccage 

 (Calvados), date back to times anterior to the " coal- 

 growths," and have continued to form part of the 

 earth's terrestrial surface ever since. The total 

 absence of all secondary and tertiary deposits over 

 any of the numerous islands which occupy the 

 angle between the Cotentin and Finisterre, shows 

 that it was originally part of the same raised area. 

 The Channel Islands, and the numerous group of 

 rocks, such as the " Roches Douvres," " Les Min- 

 quiers," and the Chausey islands, are the higher 

 portions of this subsided land. It is to this area 

 — which was not disturbed throughout the later 

 half of the palaeozoic period, nor through those of 

 our oolitic, cretaceous, and nummulitic deposits, 

 which formed the northern boundary for the old 

 marine channel of the Loire valley, which was not 

 affected by the changes which took place in the 

 northern hemisphere during the later pliocene 

 period — that we accordingly find that the earlier 

 facies of the Atlantic fauna still belongs. 



In the great Mediterranean basin we have the 

 older sea-beds and their contents ; taken by itself, 

 part of this early fauna has disappeared or died 

 out, and part survives either there or elsewhere ; 



