NO. 5 TELESCOPING OF THE CETACEAN SKULL 49 



the condition found in ordinary mammals. That such may not be 

 the case, however, is indicated by the fact that the posterior opening 

 of the antorbital canal lies under the anterior border of the orbit in 

 the Delphinimv in a position (pi. i, fig. la, a. o. for.) essentially 

 the same as that which may be seen in a sea-lion (pi. 2, fig. 2a, a. 0. 

 for.), while in the skulls with more anteriorly placed orbit the orifice 

 of the canal usually though not always lies behind the position which 

 it normally occupies with regard to the orbit. This would appear 

 to show that a readjustment of parts had taken place (most con- 

 spicuous in Platanista) , a process representing a higher degree of 

 specialization than that indicated by a greater pushing backward of 

 the orbit without readjustment of relative positions. The form of 

 the rostrum is variable and of little importance for distinguishing 

 groups higher than genera. This typical subfamily includes the 

 great majority of both living and fossil members of the family. The 

 recent genera are so well understood that they do not require special 

 mention here. Among the fossils which I would refer without too 

 great hesitation to the Dclphinince as thus restricted are those which 

 have formed the bases of the following generic names: Acrodclphis, 

 Chanipsodelphis, DelpJiinodon (as understood by True, Proc. Biol. 

 Soc. Washington, Vol. 24, pp. 37-38, February 24, 191 1; crowns 

 of posterior teeth with a broadened inner portion suggesting that 

 which occurs in the living Inia.), Heterodelphis, Lophocetus, Palceo- 

 phocccna, Palccoziphius, Physeterula, Physodon of Lydekker 1893 

 (probably not of Gervais 1872), Pithanodclphis, Pomatodclphis (may 

 be referable to the Iniidcu). Others which may belong here are: 

 Cetorhynchiis, Dclphinavus, Dclphmopsis, Dinoziphius (teeth sug- 

 gesting those of a very large Orcinus), Hesperocctits, Iniopsis, Ixa- 

 canthus, Phoccrnopsis, P rise odd phinus, Profophocccna. The names 

 in this second list are, however, based on such fragmentary material 

 that no clear idea can at present be formed regarding the animals 

 to which they are applied. 



Eurhijiodclphinincc. — The genus Eurhinodclphis has been placed 

 in a special group, principally on account of the supposed forward 

 extension of the intermaxillary in front of the maxillary to form the 

 entire anterior third of the greatly elongated beak. In other respects 

 there appear to be few highly exceptional peculiarities to separate the 

 genus from ordinary delphinids. While such a development of the 

 intermaxillary would undoubtedly be reason for regarding the animal 

 as the representative of a distinct subfamily the evidence for its 

 occurrence is inconclusive. J\Ir. Remington Kellogg has called my 



