120 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 105 



34.6 mm. in total length and the roots of the same teeth from 16 to 

 26 mm. With the exception of the pair of teeth at the extremity and 

 seven additional teeth on each side, the teeth were dislodged from the 

 alveolae on both sides of the rostrum. Fortunately, differences in the 

 size, depth, and conformation of the empty alveolae made it possible to 

 place with reasonable certainty the teeth found in the adjacent matrix 

 in the corresponding alveolae. Nevertheless, no teeth were found that 

 matched five alveolae on each side of the rostrum, although it is quite 

 likely that two additional teeth for which the crowns alone 

 were found were originally lodged in the rostrum. 



In the mandibles, however, all of the teeth except one in the left 

 mandible were dislodged from the alveolae. When the teeth were 

 fitted to the corresponding mandibular alveolae, no teeth were found 

 for two alveolae in the right mandible and one in the left mandible. 



The dental formula was originally: 



R.27-L.26 

 R.26-L.26 



Although the crowns of most of the teeth in both the upper and lower 

 jaws were worn to varying degrees, some at least are sufficiently 

 complete to show that the crowns curved inward toward the apex. 

 The inner surface of the crown above the base was somewhat rugose, 

 although the black enamel elsewhere on the crown is essentially 

 smooth. None of these teeth exhibit smj trace of accessory cusps 

 or tubercles. The basal margin of the enamel crown is hregularly 

 curved, but no cingulum is developed. The root on most of the 

 teeth appears to have been slightly constricted immediately below 

 the enamel crown. The extremities of the roots of most of the teeth 

 are bent backward. All of the teeth in the rostrum with the exception 

 of four or five of the posterior ones have the roots noticeably expanded 

 below the crown and tapered toward the extremity. 



On this fossil skull the anterior teeth and their alveolae are the 

 largest in each tooth row; the teeth and their alveolae progressively 

 diminish in size toward the posterior end of the tooth row. The teeth 

 and alveolae of Inia geqffrensis, however, increase in size from the 

 anterior to near the posterior end of the tooth row and the anterior 

 teeth have rather small recurved crowns with rugose or finely striated 

 enamel. The seven hindmost teeth of Inia have the crowns and the 

 roots widened transversely, the enamel crown of each consisting of 

 an outer low blunt pointed cusp and a flattened rugose internal shelf 

 that occupies about half of the transverse width of the crown. 



The 10 anterior teeth on each side of the rostrum are separated by 

 interspaces of varying widths, and the remainder of the teeth are 



