18 PROCEEDINGS OF THE NATIONAL MUSEUM voi„ 6!> 



additions and corrections as may be ascertained from the portions 

 of the above-mentioned skull already exposed. The ventral surface 

 of the rostrum is formed almost entirely by the maxillae which meet 

 mesially in a linear suture at the level of the anterior margins of 

 the palatines and continue forward in contact for a distance of 45 

 mm. Avhere they separate to allow the axial ridge of the vomer to 

 appear between them. Something like 32 teeth were lodged in each 

 maxilla and 8 in each premaxilla, of which the most anterior one 

 is greatly elongated and projects forward. The extremity of the 

 rostrum of the second skull is missing and the premaxillae are not 

 visible from a ventral view on that portion of the rostrum which is 

 preserved. The maxillae broaden from their anterior extremities to 

 the antorbital notches. The convexness of the ventral surface of 

 each maxilla between the tooth rows coincides almost exactly with 

 the obliquity of the dorso-lateral surface and the concaveness of the 

 basal portion is coextensive with the rounded outer border. The 

 ventral orifice of the infraorbital canal is bounded by the maxilla 

 and lachrymal. 



The lachrymal is elongate, ankylosed to the anterior margin of 

 the supraorbital process of the frontal, and contributes the posterior 

 and outer borders of the ventral orifice of the infraorbital canal; it 

 is sheathed dorsally by the apophysis of the maxilla and is separated 

 by an interval of not more than 9 mm. from the extremity of the 

 orbitosphenoid. In conjunction with the jugal it forms the lower 

 border of the antorbital notch. Below this notch the lachrymal is 

 so intimately fused with the jugal that the exact limits of these two 

 bones can not be determined. As regards shape and relations with 

 the surrounding bones, the lachrymal bears a much closer resem- 

 blance to that of Delphinodon dividum than to Sotdlia tucuxi. The 

 skulls of a number of living porpoises, particularly Steno rostratus^ 

 Lissodelphis horealis^ and DelphiTvas delphis^ all have a lachrymal 

 like that of Sotalia, but curiously enough Phocaena phoccena^ whose 

 skull otherwise is quite unlike these fossils, has a lachrymal of this 



type. 



Fortunately the entire styliform process of the right jugal is pre- 

 served on the first skull. (PI, 4.) The anterior extremity of the 

 jugal consists of a small more or less triangular body, which is deeply 

 mortised into the ventral surface of the maxilla internal to the antor- 

 bital notch and its posterior margin is ankylosed to the large 

 lachrymal bone. From the body of the jugal a long slender and 

 almost threadlike styliform process projects backward below the 

 orbit and probably was attached originally bj'^ a ligament to the 

 anterior extremity of the zygomatic process. 



When the skull of Kentriodon pernix is contrasted with skulls of 

 living porpoises, especially Sotalia tucuxi^ Lissodelphis horealis, Steno 



