THE CHIEF COLEOPTEROUS FAUNAE. 



19 



the elucidation of the distribution of animal life, nor does it fol- 

 low that because we see certain great divisions in terrestrial dis- 

 tribution, the same number and the same local distribution is to 

 be found in them also ; greater latitude and extent of range must 

 be allowed to marine animals, and especially to fishes (the birds of 

 the sea), than to land animals. The difference in their conditions 

 of life in the sea is less than on land. Geological changes, such 

 as the opening of the Isthmus of Panama and the Isthmus of 

 Suez, have a more important bearing upon their distribution than 

 upon those of land animals, inasmuch as the opening of a door to 

 admit a new element is more important than shutting it after it 

 has been already admitted. The knowledge that such events have 

 taken place, however, enables us to reconcile the occurrence of 

 marine animals in places otherwise difficult of explanation, as, for 

 example, Saurus atlanticus, both at Madeira and Zanzibar. With 

 the help of such aids I by no means despair of being able to show 

 that a similar distribution, in the main, exists in marine ani- 

 mals to that in terrestrial ; not exactly placed alike, but proceeding 

 from the same causes, and the deviations traceable to the different 

 treatment, conditions and events to which they have been sub- 

 jected. Their distribution must be studied (and happily we have 

 the means of doing so) more in connexion with their geological 

 history and the fossil remains of their ancestors. It is not my 

 present business to attempt to do this ; and I shall not do more 

 than indicate the line of argument which such considerations, at 

 first sight, seem likely to lead to. Take the Sea-perches, the 

 Percidae (not merely the genus Serranus as now understood, but 

 the group of allied genera of which it may be said to be the type), 

 a group containing the first dozen species in Dr. Giinther's list. 

 Beginning in the Chalk with genera which are now all extinct, 

 increasing in the Eocene, so that half of the genera now survive 

 and are established in the Newer Tertiary, so that all the genera 

 now existing were then present in England, that type would ap- 

 pear to be properly microtypal. 



The sea-shells being for the most part dependent on the lands 

 on whose shores they live, and therefore bound to them, are safer 

 and more direct indications of the character of these lands than the 

 fishes ; and their own stirps generally corresponds with that of the 

 terrestrial inhabitants, although, from the causes already alluded 

 to, they are sometimes exposed to diverging influences from which 

 the latter are free. We have as yet, so far as I know,, no list of 



2* 



