ART. 26 REMAINS OF FOSSIL PORPOISES KELLOGG 9 



nasals are nearly as large as the exposed portions of the frontals on 

 the vertex, and the enamel-covered crowns of the teeth are antero- 

 posteriorly compressed and rather slender. 



This form is best characterized by the exceedingly long attenuate 

 rostrum which comprises four-fifths of the total length of the skull. 

 According to Abel ^^ the premaxilla« by themselves form more than 

 half of the rostrum of an Eurhinodelipliis skull. No trace of a suture 

 between the maxilla and the premaxilla in a position corresponding 

 to that shown by Abel could be made out on any of the specimens 

 from the Calvert formation. A shallow gi'oove which probably con- 

 veyed some nerve or blood vessel is present in the same relative 

 position on the lateral face of the maxilla. Anterior to the maxil- 

 lar}^ notches the premaxillae are thick and convex; they decrease in 

 breadth and in height toward the terminal portion of the rostrum. 

 The inner margins become closely appressed to one another at a 

 point 100 mm. in front of the maxillary notches and continue in 

 contact to the extremity of the rostrum. The raised convex portions 

 of the premaxillae do not parallel one another throughout the entire 

 length of the rostrum, but spread apart rather abruptly in front 

 of the maxillary notches. In this region they form the outer margin 

 of the concave and flattened internal portions of the premaxillae, 

 and in consequence of their tapering these elevated convex borders 

 disappear in front of the nasals. The premaxillae commence to 

 expand horizontally in front of the nasal bones and attain their 

 maximum breadth at the level of the anterior margins of the nasal 

 apertures. In front of the nares there is an oval concavity on each 

 premaxilla. The posterior end of each premaxilla is abruptly nar- 

 rowed along the external margin of the nasal. The premaxillary 

 foramina are moderately large and situated posterior the maxillary 

 ones. Each of these foramina open into two grooves. One of these 

 is broad and deep and extends transversely across the premaxilla to 

 its internal margin; the other, a longitudinal groove, which is con- 

 tinued backward to a point in front of the nasal, lies between the 

 concave internal and the convex external portions of the premaxilla. 

 Anterior to the transverse groove the internal surface of the pre- 

 maxilla is somewhat flattened; this area narrows rapidly and finally 

 disappears under the raised convex outer strip. 



The premaxillae approximate each other so closely anterior to 

 the maxillary notches that the mesorostral gutter is completely 

 roofed over. Distally, the floor of the mesorostral gutter is formed 

 entirely by the premaxillae which meet mesially and ventrally in a 

 linear suture at a point slightly more than half way to the tip of 



"Abel, C, Les dauphins longlrostres du Bold^rlen (Mlocfene supfirieur) des environs 

 d'Anvers. Mem. Mas. roy. d'hist. nat. de Belgique, vol. 1, p. 65, 1901; vol. 3, p. 117, 

 1905. 



9119—25 3 



