48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



chus, Pontivaga, Pontoplanodes, Proinia. No extinct porpoise refer- 

 able with any high degree of probabihty to the family has yet been 

 found outside of South America. The living Lipotcs of China is the 

 only cetacean, recent or fossil, definitely known to represent the group 

 in the Northern Hemisphere or in the Old World. Various extinct 

 European genera, such as Champso del phis, CyrtodelphU, and Acro- 

 delphis have been supposed to be related to Inia, chiefly because of the 

 presence of a deep longitudinal groove on each side of the under 

 surface of the mandible. While some of these porpoises may eventu- 

 ally prove to be iniids it must be remembered that the development 

 of grooves, in both mandible and beak, appears to be merely a general 

 though not universal tendency in dolphins with slender rostrum and 

 long symphysis. Among living forms this grooving tendency is best 

 developed in Stcnodclphis. Its next degree is found in the distantly 

 related Platanista. In Lipotes and Inia it is very slightly indicated, 

 though these genera are more nearly related to Stenodclphis than any 

 of the three is to Platanista. By itself, therefore, this feature is not 

 an index to affinity. The presence of Lipotes in the Old World makes 

 the eventual discovery of extinct members of the subfamily appear 

 certain ; but their positive identification will depend on the finding 

 of material sufficiently well preserved to show the true structure of 

 the pterygoid and maxillary as well as the size of the temporal fossa 

 and the extent to which the frontal participates in forming the lateral 

 wall of the braincase. 



DelphinincB. — After removal of Inia and Lipotes as a family, and 

 of Stcnodelphis, Delphinapteriis, Monodon, and, provisionally, Eurhi- 

 nodelphis, as the representatives of four subfamilies, the dolphins 

 become a rather compact group chiefly characterized by the high 

 degree of telescoping of the braincase, the small temporal fossa, the 

 small pterygoid reduplicated on its inner side only, and not spreading 

 over the alisphenoid ; teeth normally-growing (never tusk-like); 

 posterior orifice of antorbital canal usually formed by maxillary alone, 

 though sometimes (Lissodclphis, Ncophoccrna) its lower edge is nar- 

 rowly touched by the palatine. The orbits are situated so far pos- 

 teriorly as to lie in the same transverse plane as the narial passages. 

 Since the narial passages have been moved as far back as the brain 

 will allow, it seems at first sight as though tlie equally posterior posi- 

 tion of the orbits might be regarded as a feature of high specialization 

 in comparison with the more anterior position which they occupy in 

 Monodon, Delphinapterus, the iniids, and even more conspicuously 

 in Platanista, a position which appears to be less of a departure from 



