204 AMERICAN JOURNAL 



— one of the latter belonging to the British, and not to the 

 New England form. 



"Of the blending of the temperate and tropical faunas on 

 the peninsula of Lower California, we are still in ignorance. 

 All we know is, that at Margarita Bay the shells are still 

 tropical, and that at Cerros Island they are strangely in- 

 termixed. There is peculiar evidence of connection between 

 the faunas of the peninsula and of South America, not only 

 in the land-shells, but in some of the marine forms." 



Mr. Y. B. Meek, in his "Check List of the Miocene Inverte- 

 brate Fossils of North America," (" Smithsonian Miscel. Coll.," 

 1864,) has the following note regarding Dr. Carpenter's opin- 

 ion as to the identity of Miocene shells of the Pacific slope 

 with living species: — 



"The extensive and critical knowledge of the living Mol- 

 lusks of the Western Coast of North America, possessed by 

 this able conchologist, renders his remarks on the relations of 

 Tertiary and existing species of that region unusually inter- 

 esting to the palaeontologist. It is to be regretted, however, 

 that his comparisons were, in most cases, necessarily made 

 with very imperfect figures of the fossil species ; the type speci- 

 mens not being accessible at the time he was in this country. 

 Hence, his suggestions that so large a proportion of the Mio- 

 cene shells of the Pacific slope are, probably, identical with 

 living species, should not be too hastily accepted. Particu- 

 larly since the questions involved are of far greater import- 

 ance than that of the mere specific difference or identity of 

 certain forms, for, if wrongly decided, they may lead to very 

 erroneous conclusions in regard to the age of these tertiary 

 deposits ; while they have a direct and important bearing on 

 the discussions respecting the duration of specific types in 

 time. Consequently, I have carefully compared the types of 

 Mr. Conrad's Western Coast Tertiary species with their living 

 representatives, in all cases where authentic examples of each 

 were at hand, and give the results of these comparisons under 

 each of the species in these notes. 



"In most of these cases, it will be observed, I have arrived 

 at the conclusion that the fossil shells are distinct species from 

 the recent. This accords with the conclusions, in many cases, 

 adopted by those who have, of late years, instituted careful 

 comparison of the Miocene species formerly supposed to be 

 identical with living forms." 



