CfO CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Not more than seven marine types are known from the Rodeo. The 

 complete list of species is as follows: 



Ostrea lurida Conrad Tagelus calif ornianus (Conrad) 



Mytilus edulis Linnaeus Epitomum hindsu (Carpenter) 



Cryptomya calif ornica (Conrad) Balanus, sp. 

 Cardium corbis (Martyn) 



All the marine species of the Rodeo-Pleistocene are still living on the 

 Pacific Coast, and with the exception of Tagelus californianus all are 

 found in the vicinity of San Francisco Bay. This species is now limited 

 to the relatively warm waters south of Santa Barbara. All of the Rodeo 

 species are now typical marine forms, but may also appear in estuaries. 

 These Pleistocene beds were presumably deposited during a period of 

 relatively warm climate, and may therefore be approximatly contempor- 

 aneous with the upper San Pedro Pleistocene of Arnold. 



Fossil bones of mammals and birds have been found at several hori- 

 zons in the Rodeo formation. Remains of Elephas are known from 

 the shell layers at the base of the section. The vertebrate fauna in- 

 cludes the following forms: 



Equus, sp. (possibly new) Felis, near atrox Leidy 



Bison, near antiquus Leidy Smilodon?, sp. 



Elephas columbi Falconer ^cmophorus occidentalis 

 Camelid (possibly new) (Lawrence) 



Mylodon, sp. 



The mammal fauna of Rodeo is not closely comparable with that of 

 any well-known stage on this coast. The camel and the horse do not 

 correspond to the species of Rancho La Brea. but later collections may 

 show that the fauna is not widely different in stage from that of 

 Rancho La Brea. 



As is pointed out above, the contrast in the lithology of 

 the Millerton and Tomales formations is striking and the 

 unconformity between the two deposits is likewise well 

 marked. As was stated in the introduction, the evaluation 

 of an unconformity in a Rift Zone area is a difficult one, as 

 events happen here with startling- suddenness. Although the 

 writer has considered this carefully, several facts cause him 

 to believe that this unconformity may represent a long period 

 of Pleistocene time, and that the Millerton formation was de- 

 posited during one warm epoch — possibly an interglacial 

 stage — and the Tomales formation during a later warm 

 epoch. When the fauna of the Millerton is studied, the ab- 

 sence of such genera as Haliotis Echinarachnius, and other 

 forms characteristic of an open coast, is a noteworthy feature. 

 The forms composing the fauna are, on the other hand, such 

 as can live in land-locked bays. The character of the lith- 

 ology and the sudden changes in the lithology of the Mill- 

 erton formation, such as the mixture of conglomerates and 



