A CONTRIBUTION TO THE KNOWLEDGE OF THE EXTINCT 

 SIRENIAN DESMOSTYLUS HESPERUS MARSH. 



By Oliver P. Hay, 



Research Associate of the Carnegie Institution of Washington. 



The genus Des^nostylus has been the subject of a number of papers 

 and its position among the mammals a matter of some dispute. The 

 genus was described by Marsh in 1888.^ Exactly what parts of the 

 animal Marsh had at his disposal the writer does not know. There 

 were some teeth or parts of them; and a lumbar vertebra is men- 

 tioned as being one of the best preserved specimens. His figures 

 are views of a part of one tooth. The materials had been found in 

 Alameda County, California; and, according to Marsh's knowledge, 

 had been associated with a morotherium, a mastodon, a camel, and 

 one or more extinct species of horses. All these were regarded by 

 Marsh as indicating the Pliocene age of the animal. He referred the 

 genus Desmostylus to the Sirenia. 



In 1891 Flower arid Lydekker ^ mentioned the genus and referred 

 it to the Halicoridje. The next discussion of the genus appears to 

 have been that of Prof. H. F. Osborn,^ in 1902. Osborn's remarks 

 were occasioned by a paper pubUshed by Yoshiwara and Iwasaki.^ 

 This last mentioned paper will be frequently referred to in the present 

 article. In Osborn's communication there was incorporated a note 

 sent him by Prof. John C. Merriam, of the University of California, 

 in which the latter discussed the geographical range of the genus. 

 He informs us that besides the specimens of teeth in Marsh's hands 

 there were others known to him. One of these had been found in 

 "Canores Canon, in the foothills of the west side of the lower end of 

 the San Joaquin Valley." Another tooth, in the museum of the Cali- 

 fornia Academy of Science, was of unknown origin. A third was in 

 the hands of the late Professor Condon of the University of Oregon 

 and had been picked up on the beach of Yaquina Bay, Oregon. 

 Merriam stated that the Californian specimen appeared to have come 



> Amer. Journ. Sci., scr. 3, vol. 35, pp. 94-96, figs. 1-3. 



» Mammals, living aud extiact, p. 22.S. 



» Science, n. s., vol. 16, pp. 713, 714. 



« Journ. College Science, Imp. Univ. Tokyo, vol. 16, art. 6, pp. 1-13, pis. 1-3, 4 text figs. 



Proceedings U.S. National Museum, Vol. 49~No. 2113. 



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