2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 87 



below the top of the Temblor formation ; the Vedder zone has a 

 maximum thickness of 85 feet in the Mount Poso area and under- 

 lying these sands are 550 to 650 feet of marine sediments, making a 

 total thickness of 2,000 to 2,100 feet. The Vedder horizon, according 

 to G. M. Cunningham, is older than the Barker's ranch locality which 

 has been described by F. M. Anderson."" It is the opinion of Mr. 

 Barbat that this horizon should be correlated with the Vaqueros 

 formation which is thought to be equivalent in time with the Bur- 

 digalian [ = Langhian] stage of the European Tertiary. 



DIAGNOSIS 



As compared with Argyrocettis patagonicus Lydekker," this spe- 

 cies is characterized by an elevated vertex formed for the most part 

 by the elongated nasals and the hinder ends of the thickened pre- 

 maxillaries, the mesorostral gutter is narrower, and the hamular 

 processes of the pterygoids are conspicuously prolonged backward. 

 It agrees with A. patagonicus in having a broad, concave D shaped 

 supraoccipital shield, in having the outer borders of the maxillaries 

 at the base of the rostrum slope downward, and in having the vertex 

 contracted antero-posteriorly. 



SKULL 



Dorsal vietv. — Although the major portion of the rostrum is de- 

 stroyed it is obvious that this skull belongs to one of the long-beaked 

 porpoises. The dorsal surface of the skull is constituted almost en- 

 tirely by the maxillaries and the premaxillaries ; the hinder extremi- 

 ties of the premaxillaries, the nasals, and the small wedgelike bone 

 (presumably frontal) form the vertex of the skull. The maxillary 

 notches are well marked. From the dorsal aspect the maxillaries are 

 seen to increase in width from the broken extremity of the rostrum 

 posteriorly. When they reach the level of the maxillary notches the 

 maxillaries are thrust backward over the supraorbital processes of 

 the frontals and expanded laterally to form the so-called frontal 

 plates. These thin plates of the maxillaries and the corresponding 

 underlying lateral extensions of the frontals roof over the temporal 



^ Anderson, F. M., The Neocene deposits of Kern River, California, and the 

 Temblor basin. Proc. California Acad. Sci., ser. 4, vol. 3, pp. 98-100, No- 

 vember 9, 191 1. 



^ Lydekker, R. Contributions to a knowledge of the fossil vertebrates of 

 Argentina. Pt. II. Cetacean skulls from Patagonia. Anal. Mus. La Plata, vol. 2 

 for 1893, pp. 10-12, pi. 5, figs. I, la, 2, 3, 1894. 



