TRUE] REMAINS OF FOSSIL CETACEANS 455 



channels running forward. At the widest point the main grooves 

 have a breadth of 6 mm. The rounded eminence between them is 

 12 mm. broad at the middle of the symphysis. 



The alveoli are like those of the upper jaw, being somewhat 

 elliptical in outline, and are directed forward, outward, and upward. 

 At the tip of the jaw the roots of the teeth, at least, must have been 

 directed almost horizontally. A few of the posterior septa are 

 complete and are nearly as broad as the diameter of the alveoli. 

 More anteriorly they are less distinct and were probably incomplete. 

 This is especially true at the tip of the jaw, where the alveoli are 

 very close together. On.the left side about 67 alveoli can be counted, 

 which was probably nearly the full number of teeth. The dentition 



would then be about - -— = 264. 

 67-67 ^ 



The posterior portion of one of the rami is present, but lacks the 

 condyle. Mr. Case gives the length from the posterior end of the 

 symphysis to the posterior end of the ramus as 199 mm., but when 

 the fragment above mentioned is placed so as to be in contact with 

 the portion of the ramus attached to the symphysis, this length is 

 232 mm. It is certain, however, that a portion of the ramus is lack- 

 ing. When complete its length must have been considerably greater 

 than is indicated by either of the foregoing measurements. The 

 dental canal appears to have had a wide orifice, as in the Delphinidse, 

 Mesoplodon, etc., rather than as in Platanista and Inia. 



The left tympanic bulla, which is the only one preserved, is 52 

 mm. long and 30 mm. broad. The inferior surface is divided unsym- 

 metrically by a deep longitudinal furrow, the latter being nearest 

 the inner lip. This groove continues to the posterior end of the 

 bulla, where it lies between the two rounded prominences which 

 represent the termination of the outer and inner lips. The inner 

 prominence is only a little smaller than the outer one and is equally 

 rounded. The inferior surface of the inner lip and of the bottom 

 of the furrow is rugose ; the surface of the outer lip is smooth. The 

 anterior end of the bulla is acuminate. The lateral and superior 

 surfaces of the inner lip are divided by a broad, shallow groove 

 running transversely near the posterior end. A similar groove in the 

 outer lip runs in front of the sigmoid process. The inner wall of 

 the concavity of the bulla is rugose. 



The frontals were briefly described by Mr. Case, and there is 

 with the type specimen, as already mentioned, a piece about 85 mm. 

 long and 58 mm. wide, which may represent the orbital part of one 

 of these bones. After repeatedly examining it, however, I am unable 



