AKT. 19 



A MIOCENE PORPOISE FROM MARYLAND KELLOGG 



9 



fessor Lull says that the premaxillary bone is toothless. It is not 

 necessary to consider the skull of Heterodelphis leiodontus Papp ^^ in 

 this connection because the rostrum and mandibles of this porpoise 

 are considerably longer than those of Kentriodon peimix. 



The similarities and differences observable between the skulls of 

 Kentriodon pernix and Delphinodon dwidura are listed in the fol- 

 lowing tables for the convenience of those who may be interested in 

 this subject. 



Comparison of skulls of Kentriodon pernix and Delphinodon dividum Cope 



DORSAL ASPECT 



Delphinodon diiidum True 



Kentriodon pernix 



Brain case very large, broad, and al- 

 most equal in length to rostrum. 



Rostrum relatively short, strongly at- 

 tenuated, and not constricted at 

 base. 



Vertex small, more or less pentagonal. _ 



Nasals relatively large, anterior mar- 

 gin concave, and depressed ante- 

 riorly. 



Apophysis of medium size, not con- 

 spicuously produced. 



.\ntorbital notch shallow. 



Maxillary foramina situated anterior 

 to antorbital notches. 



Horizontally expanded cranial plate 

 of maxilla not wider than premaxilla 

 at level of anterior margin of respira- 

 tory passages. 



Premaxillae noticeably expanded pos- 

 terior to antorbital notches. 



Curvature of transverse crest of su- 

 praoccipital regular. 



Brain case short and narrow, about 

 five-eighths as long as rostrum. 



Rostrum relatively long, slender, and 

 slightly constricted at base. 



Vertex small, more or less pentagonal. 



Nasals relatively large, anterior margin 

 deeply notched, and elevated ante- 

 riorly. 



Apophysis large, conspicuously pro- 

 duced. 



Antorbital notch deep and narrow. 



Maxillary foramina situated posterior 

 to antorbital notches. 



Horizontally expanded cranial plate of 

 maxilla wider than premaxilla at level 

 of anterior margin of respiratory pas- 

 sages. 



Premaxillae not noticeably expanded 

 posterior to antorbital notches. 



Curvature of transverse crest of supra- 

 occipital irregular. 



^" Papp, C. von, Heterodelphis leiodontus nova forma aus den Miocenen Schichten des 

 Comitates Sopron in Ungarn. Mitteil. Jalirb. Konigl., Ungar. Geol. Anstalt, Budapest, 

 vol. 14, Heft 2, pp. 25-60, pis. 5-6, text figs. 1-10, 1905. 



2994—27 2 



