ARNOLD — THE PALEONTOLOGY AND STEATIGKAPHY OF SAN PEDEO. 67 



waters of the lagoons. Such is the case, but it is a noticeable fact that in the upper 

 San Pedro fauna 14.2 per cent, are species which are found living at the present time 

 only south of San Pedro. Not only is this true, but of the species in the upper San 

 Pedro fauna which are now living at San Pedro a lai'ge number are best suited for 

 southern conditions. 



Although 6.1 per cent, of the upper San Pedro fauna ai'e found now living 

 only north of San Pedro, these northern species are only very rarely found in the 

 upper San Pedro deposits. On the other hand, not only are most of the southern 

 forms common in the upper San Pedro series, but the whole fauna has a semitropical 

 aspect. Such sp)ecies as Cardium elatum, Area lahiata, Peden dentatus, Mactra 

 exoleta, Venus giiidia, Murex keanus, Eiqjleura muriciformis., Cancellaria tritonidea, 

 and Bulla jmnctalata give this fauna its tropical character. The evidence offered by 

 the southern forms outweighs the evidence of the northern species in another respect, 

 for it would require a great change in climate from the conditions prevalent during 

 later Pliocene times to cause these southern sjiecies to migrate northward to the San 

 Pedro region; while this same change in climate would not so visibly affect the 

 northern species, for they could simply migrate into deep water, where the conditions 

 would more nearly approximate the boreal. This latter has been the case with such 

 species as Lucina acutilineata, Chrysodomus tabulatus, Solariella cidaris and Solnriella 

 peramabilis, which now inhabit northern waters, near shore, but which have been 

 dredged in the deep water between Catalina Island and the mainland. 



The evidence offered by the upper San Pedro fauna leads to the conclusion 

 that semitropical conditions prevailed during the deposition of this formation. 

 The similarity of the fauna of these beds with that now living at San Pedro and the 

 adjacent coast makes it probable that the conditions, although more tropical than those 

 of the present time, were not extremely tropical. 



3. Relation of the Late Pliocene, Pleistocene, and Living Faunas of 



California to the Fauna of Japan. 



Great similarity exists between the late Tertiary and Pleistocene marine in- 

 vertebrate fauna of Japan and that of the western coast of the United States. This 

 similai'ity is shown by a comparison of the species found in the uppermost Tertiary 

 deposits in the region about Tokio and the species found in beds of similar age along 

 the Pacific coast of North America. 



Dr. Brauns' has described some of the formations in the vicinity of Tokio, and 

 has given lists and descriptions of the fossils found in these formations. Dr. Brauns 

 thinks that the deposits he has examined are of the uppermost Tertiary. His lists of 

 fossils lead to that conclusion, if one compares them with the fauna of the later Plio- 

 cene of California. Many of the Japanese species have counterparts in species found 

 in the San Pedro deposits. Such species, for example, as Lucina borealls, Cylichna 

 cylindracea, and Fecten yessoensis are closely related, if not identical, with the west 



1 Geology of the Environs of Tokio. By David Brauns. Mem. Sci. Dept. Univ. of Tokio, No. 4, 1881, pp. 27, 61. 



