OF SANTO DOMIISTGO. 



101 



LIVING. 



LIVING. 



GENEKA. 



GENERA. 



Donax 



Venus 



Gliione . . . . 

 Callista. . . . 

 Caryatis . . . 

 Cyclina . . . . 

 Cardium . . . 

 Chama . . . . 

 Lucina. . . . . 

 Loripes. . . . 



Mysia 



Erycina . . . 

 (Jouldia . . . 

 Crassatella. 

 Cardita. . . . 

 Crenella. . . 



1 Pacific. 



1 of W. I. fossil ill 

 U. B. Miocene. 



Lithophagus . 



Avicula 



Area 



Axina;a 



Liiiioijsis 



Nucula 



Leda 



Yoldia 



Pecten 



Janira 



Pleuronectes . 

 Spondyhis . . . 



Plicatula 



Anemia 



Ostrea 



1 Brazil. 



1 Europe. 



It is but just to myself to add here that all of this memoir except the Palaion- 

 tology, was written in Santo Domingo, and that this table, the last part prepared of 

 all, has surprised me with the very unexpected results it ofters. According- to the 

 rule proposed by Lyell, I should pronounce the fossils Pliocene. But the presence 

 of several antique types among the genera disinclines me to the step. With two 

 hundred and seventeen supposed extinct species and ninety-seven known to be living, 

 the only change that can take place in our proportion is the transfer of some of the 

 former to the latter category. Many of the new species are minute, and they may 

 yet be discovered living. Should such detailed examinations of the coast of Santo 

 Domingo ever be made as that in Cuba, of which we have the results in La Sagras' 

 tine work, doubtless many of our small fossils would be discovered. On the other 

 hand, students less conservative than I have endeavored to be, may find real or 

 fancied specific differences between the fossils and the recent species with which I 

 have associated them, thereby modifying the propoilion in the opposite direction. 

 But in eithei" case, the change cannot be a large one. We will always have about 

 30 to 33 per cent, of living forms. Lyell fixes from 35 to 50 per cent, as the pro- 

 portion of tlie Pliocene, and says of the standard Miocene : — that of the Loire and 

 Gironde contains but 17 per cent. We are therefore at or near the top of the 

 Miocene. I do not yet know how far a study of the fossil-radiates of the collection 

 would influence these results, but, numerically, they are comparatively unimportant. 



I have not thought it necessary to repeat the tabulation of the distril)ution of 

 fossils among the various islands. Except that I would include nearly all the 



