354 University of California Puhlications in Geology [Vol. 12 



the posterior and mid-eentral tubercles. The specimen is, on the other 

 hand, larger than the Pg of a series figured by Dr. Matthew from the 

 Pliocene of western Nebraska, which is referred to Prosthennops 

 crassigcnis.*'^ The specimen approximates in size P5 of the Nebraska 

 series, but lacks the latter 's well developed, posteroexternal cingulum 

 and height in the anterior cones. F. serus is stated to be larger than 

 P. crassigensis. 



No. 23776 has somewhat the general appearance of an INI, from the 

 ]Merychipi3us zone of Coalinga,*- measuring 26.2 mm. by 15.9 mm. 

 though laekinii' in the molariform characters of heel and large external 

 cingulum. 



Specimen no. 23776 is without tlie development of the tubercles of 

 the inner side as well as the anterior and large posterior shelves, and 

 is more strongly bunodont than a Pg from the Rattlesnake referred 

 to Prosthennops, which measures 16 mm. anteroposteriorly by 11 mm. 

 transversely. A great dissimilarity between these two forms has been 

 noted already in the comparison of the upper teeth. 



Lower cheek tooth, no. 23775 (fig. 62), possesses a central pair of 

 transverse cones lying between portions of an anterior and of an 

 inflected posterior pair. The specimen evidently represents the last 

 molar. It is low-crowned, and the shallow transverse valleys are 

 without accessory tubercles. The tooth apparently corresponds in 

 size with the last molar of the lower jaw series (no. 23370). 



PLATYGONUS?, sp. 



Material. — A large canine, no. 23439, and a much more slender canine of e'qual 

 length, no. 23440, both from the lower left side of the jaw (figs. 64, 65), Univ. 

 Calif, loc. 3269. Both specimens in Univ. Calif. Coll. Vert. Pal. 



Description. — The larger specimen (no. 23439) is robust, triangular 

 in cross-section, and well recurved. The narrow anterior edge is some- 

 what rounded. A flat, sharp-edged surface is worn into the posterior 

 side and cuts diagonally across the alveolar portion. The inner side 

 is slightly grooved, and is narrower than the outer. The outer side 

 is marked along the median line by a well defined swelling which is 

 continuous with the root. A corresponding groove occurs on the inner 

 side, and is discernible in the root but is interrupted in the region 

 of the alveolus. 



11 Matthew, Wm. D., and Cook, Harold J. A Pliocene Fauna from Western 

 Nebraska. Bull. Am. Mus. Nat. Hist., vol. 26, p. 390, 1909. 



Merriam, J. C. Tertiary Vertebrate Faunas of the North Coalinga Region 

 of California. T. A. P. S., vol. 12, pt. 3, p. 12, 191.5. 



