lO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 87 



prise the major portion of the large vertex, the area of the exposed 

 portions of the frontals on the vertex being considerably larger than 

 that of the two nasals, a small interparietal is present, the zygomatic 

 process is relatively short and robust, and the roots of the teeth arc 

 shaped somewhat like a heraldic battle axe. In so far as our present 

 knowledge goes the proportions, relations, and structural peculiari- 

 ties of the several elements entering into the composition of the brain- 

 case and rostrum of Schicodelphis are sufficiently pronounced to 

 eliminate this genus from consideration. 



The long-beaked porpoise, Argyrocctus patagonicus!^ from the 

 Lower Miocene Patagonian marine formation at Castillo, opposite 

 Trelew, on the coast of Chubut Territory, Argentine Republic, re- 

 sembles this California skull somewhat, for the vertex is contracted 

 antero-posteriorly and the backward rostral thrust has carried the 

 maxillary to the supraoccipital, but the two nasals are about equivalent 

 in area to that of the exposed portions of the frontals on the vertex 

 and the mesorostral gutter is relatively wide. This skull, unfortu- 

 nately, is imperfectly preserved, both zygomatic processes being in- 

 complete, the supraorbital processes are broken ofif, and the hinder 

 ends of the premaxillaries are missing. The shape of the supra- 

 occipital shield, the elevation of the vertex, and the proportions of 

 the skull of Argyrocetiis patagonicus approximate in the main the 

 skull from California. These resemblances seem to warrant the ten- 

 tative allocation of the California skull to the genus Argyrocetus, 

 though this is done with considerable hesitation, since the material 

 upon which both species are based is quite fragmentary. 



TEETH 



The crown of a single tooth, presumably from the right maxillary, 

 is embedded in the matrix 12 mm. in front of the broken extremity 

 of the rostrum. The crown of this tooth is lanceolate in outline, it 

 curves outward and then inward, and is flattened transversely. The 

 anterior and posterior margins of the crown are rounded and not 

 carinate, and the enamel is essentially smooth. The hinder end of 

 the maxillary tooth row lies 60 mm. in front of the maxillary notch. 



' 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, 18Q4. 



