20 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 



these two species that, while the Ammonitella appears to be ap- 

 proaching extinction as indicated by its restricted habitat, the 

 other species found with it, especially the E. fidelis, has not only 

 survived the "remarkable vicissitudes or physical conditions" 

 speci'fied, but has evolved or been modified into diverse forms 

 which have been distributed over a large area of the Pacific 

 Coast region, and are known under various specific names. 



The immense numbers of fossil vertebrates representing a 

 large number of species and genera, which have been found in 

 the fresh water basins of Miocene age, are fairly bewildering 

 and intensely interesting to the zoologist, but being mostly re- 

 stricted to the regions lying East of the Sierras, and not found 

 in California will be passed over. 



One of the most interesting fossil vertebrates found in Cali- 

 fornia is a unique, amphibious mammal allied to the Dugong, 

 which was discovered by the writer some twenty-five vears ago. 

 It is very distinct from anything before discovered in this 

 country, and puzzled the paleontologists of America until the 

 late Professor O. C. Marsh determined its affinities and described 

 it as the only known species of an entirely new genus. The 

 writer discovered portions of the fossil remains of dift'erent in- 

 dividuals in three different localities in Alameda county, Cali- 

 fornia, and the animal has not been found elsewhere, so far as 

 known. Professor Marsh's description, and the illustration as 

 published in the American Journal' of Science, Vol. XXXV, 

 Jan. 1888, is here reproduced. "Notice of a new FossiIv Si- 

 RENIAN, FROM CALIFORNIA; bv O. C. Marsh. 



./^i 



Fio-. I. 



Fig. 2. 



Fig". ,3. 



Fig". I. Part of tooth of Dcsinosfylus hcspcnts. iNIarsli ; end view. 

 Fig. 2. The same specimen ; seen from above. 

 Fig. 3. The same specimen ; inner surface. 

 All the figures are natural size. 



