404 



University of California Publications. 



[Geology 



OCCURRENCE 



Particular attention has already been called 2 to the fact that 

 all Desmostylus material of which definite information could be 

 obtained has been found in marine beds. This statement is, 

 however, not in accord with that of Marsh, according to whom 

 the type material was found in association with remains of 

 mastodon, camel, a large edentate, and one or more species 

 of horse. Since the publication of his note on this subject it 

 has been the writer's privilege to examine Marsh's type of 

 Desmostylus, through the courtesy of Professor Richard S. Lull, 

 of Yale University. Contrary to the statement in Marsh's 

 description, it was found that the original label describes the 

 type of Desmostylus as coming from Contra Costa County, Cali- 

 fornia, where it apparently occurred in association with marine 

 Miocene invertebrates. One of the specimens is embedded in 

 rock similar to that of one phase of the marine Miocene of middle 

 California. The only objection to considering Desmostylus as 

 a marine form has, therefore, disappeared. It is to be presumed 

 that the animal may have occupied the mouths of rivers and 

 could, therefore, be found in estuary or even in river deposits. 



Within the last few years a number of occurrences have come 

 to light which indicate collectively that Desmostylus is limited 

 to a comparatively narrow geologic zone of the Tertiary, and is 

 presumably of value as a means of correlating widely separated 

 deposits. 



Numerous fragments of Desmostylus teeth have been found 

 by Mr. F. M. Anderson to the north of Coalinga, in the western 

 part of the San Joaquin Valley, in beds designated by him as 

 the Temblor formation. As nearly as can be determined, Des- 

 mostylus does not occur either above or below this zone in this 

 region. A record of an occurrence corresponding to that de- 

 scribed by Mr. Anderson was obtained by the writer some years 

 ago from a specimen in the museum of the California State 

 Mining Bureau. The location of this specimen is defined as 

 Canoes Cafion, Sec. 33, T. 22 S, R. 16 E, Mt. Diablo Base and 

 Meridian. As shown by the mapping of this region by Ralph 



? Merriam. J. C, Science, n. s., vol. 24, p. 151, 1906. 



