teue: the fossil cetacean, dorudon seeratus. 71 



and inferior surfaces of the premaxillae and the rather small orbit, one 

 may infer that it was not great. 



The frontal is represented only by the right orbital plate (Plate 2, 

 figure 2), which is in three pieces. These pieces cannot be fitted to- 

 gether, but the shape of the arch of the orbit indicates that the outer 

 free margin is complete, or nearly so. Anterior to the orbit is a triangular 

 prolongation, on a slightly lower level than the top of the orbit itself, 

 and having the surface somewhat different in texture. It is possible 

 that this triangular area was overlapped by the posterior thin end of 

 the maxilla. 



Behind the frontal no part of the upper surface of the skull is pre- 

 served, except a portion of the right parietal bone (Plate 2, figure 3). 

 This, fortunately, is complete in the median line and posteriorly, and 

 indicates the form of the occipital and sagittal crests. The distance be- 

 tween the vertex and the nasals can, however, only be estimated. 



A small piece of the squamosal (Plate 2 figure 4) from the left side 

 indicates the shape of the zygomatic process and the position of the 

 external auditory meatus. The occipital condyles are lacking, and nothing 

 can be determined regarding the inferior surface of the skull except as 

 above mentioned. 



The teeth merit a special description. As already stated, the first 

 upper incisor is lacking on both sides, the premaxillae being incomplete 

 anteriorly. A portion of the alveolus of the second upper incisor is 

 present on the left side. When complete, it measured about 22 mm. 

 in diameter longitudinally. The distance between it and the alveolus 

 of the third incisor is 29 mm. The longitudinal diameter of the latter 

 alveolus is 25 mm., and of the third incisor itself, measured on a level 

 with the top of the alveolus, 21 mm. The transverse diameter of the 

 tooth at the same point is 15 mm. As indicated by these measurements, 

 the root of the tooth is elliptical in section at its junction with the crown. 

 Only a small portion of the latter remains, but sufficient to show that 

 the enamel was strongly rugose, and that a well-defined, narrow ridge 

 extended from the base of the crown probably to the apex posteriorly. 



The alveoli of the upper incisors are connected by a narrow groove. 

 The palatal surface of each premaxilla internal to this groove is flat, and 

 is divided longitudinally in the centre by another groove, running par- 

 allel with the median border. In front of and behind the third incisor 

 the outer surface of the premaxilla is strongly compressed. In front of 

 the tooth, at a height of about 22 mm. above the palatal surface, is a 

 circular concavity, representing the position of the apex of the lower 



