ART. 14. MARYLAND FOSSIL PORPOISE KELLOGG. 17 



In Platanista^ the palatines are entirely concealed by the overlying 

 external and internal pterygoids; the latter extend forward to the 

 level of the preorbital projection of the supraorbital process. Tlie 

 vaginal plate of the internal pterygoid is sutiirally united with the 

 vomer posteriorly. The thin plate of the internal pterygoid curves 

 around the nasal passage and meets the maxilla mesally; it then 

 turns abruptly and extends forward beneath the external pterygoid. 

 That portion of the internal pterygoid which lies anterior to the nasal 

 passages is closely appressed to the palatine and the maxilla above; 

 the external margin is fused with the corresponding margin of the 

 external pterygoid. As a result a cavity is formed between the 

 internal and external pterygoids, the opening being along the keel. 

 "W-Tien the internal and external pterygoids are removed, the palatine 

 is exposed (pi. 5). The peculiar position of the palatine has been 

 pointed out and discussed by Eschricht and Anderson. It has been 

 reduced to a small elongated bone whose antero-posterior diameter 

 is about equal to the diameter of the corresponding nasal passage. 

 The palatine is closely appressed to the maxilla and these two bones 

 combined form the anterior wall of either nasal passage. Wliile 

 similar relations between the palatine, maxilla and internal ptery- 

 goid are maintained in skulls of Lipotes and /?im, the palatine, how- 

 ever, is not entirely concealed by the internal pterygoid. 



The similarities and differences obtaining between Platanista on 

 one hand, and Lipotes and Inia on the other have been fully discussed 

 above. Detailed comparisons have shown that the relations of the 

 various bones in the basicranium of this fossil skull are in agree- 

 ment with Platanista. One detail could not be satisfactorily deter- 

 mined from this fossil skull and that is the exact relations between 

 the internal pterygoid and the external pterygoid near their anterior 

 extremities. 



The thickened edge of each internal pterygoid appears in the 

 interval between the lower edge of the external pterygoid and the 

 keel of the vomer. Slit-like apertures appear on either side between 

 the keel of the vomer and the exposed edges of the internal ptery- 

 goids. It is possible that these apertures may be the result of distor- 

 tion brought about by crushing. The pyramidal cavity which is 

 thus formed on ether side of the keel is bounded on the inside by the 

 internal pterygoid, on the outside by the external pterygoid, and at 

 the rear by that portion of the former which curves around the nasal 

 passage. 



After making careful comparisons between this fossil skull and 

 those of Lipotes and /ma, it was found that differences were observ- 



