TKUE : THE FOSSIL CETACEAN, DORUDON SERRATUS. 



77 



surface vertical. The anterior and posterior articular facets are sepa- 

 rated from each other by a very broad, flat surface. The vertebrarterial 

 canal is not sunk into the side of the vertebra, but is about in line with 

 the outer edges of the articular facets. The inferior lateral process is 

 not strongly inclined backwai'd. The upper surface of the premaxillae 

 is flat, but the nasal branch strongly bent upward. The first upper pre- 

 molar is small. 



On comparing the type of Dorudon serratus Gibbes, with the type 

 of Zeuglodon brachyspondylus minor, and the small zeuglodont from Ala- 

 bama in the National Museum, I find that the Alabama specimen agrees 

 with Z. brachyspondylus minor, and without doubt represents that form. 

 Dorudon serratus, on the other hand, although of the same size, presents 

 numerous differences. These are best seen in the following parallel 

 columns : 



Dorudon serratus. 



1. Incisors smaller. 



2. Incisors differently spaced from 

 those of Z. b. m. 



3. Nasals vaulted. 



4. Premaxillae broad and convex on 



top. 



5. Premaxillae deep and flat on the 

 sides. 



6. Proximal end of nasal branch of 

 premaxillae not strongly bent up. 



7- Atlas comparatively thin. 



8. Outer expanded portion of posterior 

 articular facets of atlas oblique. 



9. Vertebrarterial canals nearly in line 

 with outer ends of articular facets. 



10. Anterior and posterior articular 

 facets of atlas separated above by 

 a narrow fiat surface. 



11. Inferior lateral process of atlas but 

 little inclined backward. 



Zeuglodon brachyspondylus minor. 



1. Incisors larger. 



2. Incisors differently spaced from 

 those of D. s. 



3. Nasals fiat. 



4. Premaxillae rather narrow and flat 

 on top. 



5. Premaxillae not so deep, and con- 

 vex on the sides. 



6. Proximal end of nasal branch of 

 premaxillae strongly bent up. 



7. Atlas thick. 



8. Outer expanded portion of posterior 

 articular facets of atlas vertical. 



9. Vertebrarterial canal much within 

 the line of the articular facets. 



10. Anterior and posterior articular 

 facets of atlas separated above by 

 a broad concave surface. 



11. Inferior lateral process of atlas 

 much inclined backward. 



Although some of the foregoing characters are doubtless to be re- 

 garded as specific, I think that, taken together, they afford sufficient 



