22 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 



abundant and interesting. It so far consists of beds of marine 

 shells, found at short intervals throughout the Coast Range and 

 the foothills of the Sierra Nevada," which contain the proper 

 proportion of living species to prove their age as relatively 

 older than the Pliocene." * * * "As the Miocene was else- 

 where the culminating point for the large and strange tertiary 

 mammals, it is altogether probable that some of them inhabited 

 portions of the dry land of California, connected with the re- 

 gions in which they were so abundant in the north ; but so far 

 the geological surveys have not been sufficient to define their 

 limits, either in time or space, within the State." 



It is possible that, in consequence of the great erosion which 

 has taken place on the surface, some of the Miocene animal re- 

 mains may have been transported from the land of the period, 

 either by the action of water or ice, and deposited in the strata 

 of more recent formations. 



The Miocene Period in California was, however, rich in the 

 number and variety of its mollusca, which are found in a good 

 state of preservation. Immense beds of fossil oysters of un- 

 rivalled size, were deposited during the period, some of the 

 shells being sixteen inches in length, and correspondingly wide ; 

 One of these beds has been found on the west shore of the 

 Colorado Desert, at an altitude of over one thousand feet ; The 

 writer found another bed of these Oysters (Ostraea Titan) near 

 the summit between the Livermore and San Joaquin valleys ; 

 They are also found near San L,uis Obispo, and in other lo- 

 calities. 



In the center of a large concretionary boulder in the Miocene 

 region of Alameda County, the writer discovered a well pre- 

 served specimen of a new species ot Pinna, figured on Plate 4, 

 of this Section, Fig. 53, and a description was published in the 

 Report of the State Mining Bureau of California for 1887, p. 

 259. (Note — For some unexplained reason the photograph and 

 drawing sent to- the State Mining Bureau with the description, 

 not used for the illustration, but a poor specimen found some 

 years later, in the Pliocene of the San Joaquin Valley was used 

 instead.) 



The original type specimen is still in the writer's collection, 

 is nearly twice the length of the specimen figured, almost perfect 

 in outline, and retains a considerable portion of the original 

 shell ; the species was afterward found in Ventura and Kern 

 counties, in deposits of Pliocene age. 



(To be Continued). 



