14 PROCEEDINGS OF THE NATIONAL. MUSEUM vol. 66 



tension of a thin plate of the frontal to underlie the maxilla. In 

 this fossa the parietal is suturally united inferiorly with the squa- 

 mosal, anteriorly and superiorly with the frontal, and posteriorly 

 with the supraoccipital. Hence the parietals are excluded from the 

 dorsal surface of the skull. When viewed from the side, the 

 condyles are seen to project beyond the plane of the exoccipitals. 

 The basicranial axis is bent downward from the axis of the beak. 



Posterior view. — This surface (pi. 4) attains its greatest breadth 

 at the level of the exoccipitals. These exoccipitals are relatively 

 large, coalesced with the supraoccipital above, and project outward 

 and backward like wings. Their external margins are rounded, but 

 are not produced so that they conceal the zygomatic processes from 

 behind. Anteriorly they are in contact with the squamosal and 

 inferiorly they unite with the basioccipital. The junction of the 

 exoccipital with the basioccipital lies internal to the deep jugular 

 incisure and crosses the falcate process of the latter. At the bottom 

 of this incisure and near the posterior margin there is a small 

 condylar foramen. The dorsal border of the exoccipital ascends 

 about half way to the upper limit of the temporal fossa. Exter- 

 nally the upper portion of the exoccipital is produced backw^ard, 

 forming a crest which follows the curvature of the temjDoral fossa. 

 This crest is continuous w^ith the corresponding border of the 

 supraoccipital and together they form the lambdoid crest. The 

 dorsal contour of the supraoccipital is evenly rounded. Between the 

 upper limits of the temporal fossae the supraoccipital is deeply con- 

 cave, but becomes somewhat flattened above the foramen magnum. 

 The greatest breadth of the supraoccipital is about equal to twice its 

 depth above the condyles. 



Because of crushing the occipital view of this cranium appears 

 slightly unsymmetrical, and the distortion lies in the direction of a 

 plane passing from the upper left-hand angle to the lower right- 

 hand angle. This distortion has affected the contour of the foramen 

 magnum to some extent, but originally it must have been suboval in 

 outline. The occipital condyles are considerably broader near the 

 apex than near the base, and slope outward and forward. The in- 

 ternal margins are concave and sharply defined, converging infe- 

 riorly. The external margins are convex and are set off from the' 

 exoccipitals by low necks. Below the condyles and internal to the 

 exoccipitals are the descending plates of the basioccipital. 



Ventral view. — In contrast to other porpoises with very long beaks 

 there is reason to believe that the distal end of the rostrum of 

 this form did not bear teeth. Of course, there is the possibility that 

 a cartilaginous ligament might have lodged the teeth on this portion 

 of the rostrum, for there is an uninterruped furrow extending from 

 the anterior-most alveolus to the extremity. In that event the teeth 



