442 SMITHSONIAN MISCEIvLANEOUS COLLECTIONS VOL. 52 



fossae, bounded above by strong ridges, and internally by the convex 

 surfaces of the parietals and squamosals. 



The similarity to Inia in the foregoing characters is close enough 

 to make it quite certain that the form is really allied to that genus, 

 but the skull presents differences of sufficient importance, in my 

 opinion, to justify its separation under a distinct generic name. 

 These differences are as follows: The free margins of the orbital 

 plates of the frontal, instead of being nearly parallel, as in Inia, 

 diverge strongly anteriorly. The greater part of the surface of the 

 plates is, furthermore, nearly horizontal, but is strongly curved down- 

 ward anteriorly, and the external free margin is not bent upward. 

 The temporal fossae appear not to have extended to or beyond the 

 line of the occipital condyles, as they do in Inia, and the region of 

 the exoccipitals is broad and flat, rather than narrow and concave, 

 as in Inia. The zygomatic process is oval and convex externally, 

 as in many of the Delphinidae, rather than rectangular and concave 

 externally, as in Inia. 



The most anterior portion of the skull which has been preserved 

 consists of the orbital plates of the frontal. These are smooth 

 superiorly, and might be considered to consist of the maxillary and 

 frontal plates consolidated, but the smoothness is, I think, due in part 

 to excessive chiseling, and the structure, as shown in section at the 

 broken edges, seems to support this view. The greater part of the 

 surface is flat, but posteriorly it becomes concave, and anteriorly 

 convex and curved downward. The plates diverge strongly, and 

 the right one is broken off a little in front of the postorbital process. 

 This process is short and rather blunt, and is directed downward. 

 Its form is, therefore, quite unlike that of Inia. The orbit, which is 

 situated well forward, appears to have been relatively quite large. 

 The free margin of the orbit is thin. 



The median processes of the frontal at the vertex are very large 

 and strongly elevated, and are squared and smooth superiorly. 

 They resemble the nasals of the Right whales. The external sur- 

 faces are vertical. The nasals and premaxillse are lacking. 



The shape of the maxillary plates can not be determined, but was 

 probably the same as in Inia, the postero-internal angle being bent up 

 so as to rest against the vertical sides of the median frontal processes. 



The position of the blowholes has been altered by vertical com- 

 pression, so that they stand above the level of the orbital plates of the 

 frontal. They are small, relatively, and are separated from each 

 other by a wide interval, which appears to indicate that the superior 

 portion of the septum has been broken off. Anteriorly, the end of 

 the large elliptical mass of the mesethmoid is seen. 



