TRUE : THE FOSSIL CETACEAN, DORUDOX SERRATUS. 67 



Cope iu 1890 remarked: — "When the Z. hrachyspondylus IMlill. is 

 better known it may be found to be referable to a distinct genus, Doryo- 

 don Gibbes" (American Naturalist, 1890, Vol. 24, page 602). 



Dames iu 1894 states that he cannot agree with Leidy in regarding 

 Zeuglodon hrachyspondylus as a synonym of Dorudon serratus, and 

 affirms that the latter is easily distinguished from Z. brachysjwiidylus 

 or Z. macrospondylus (=■ Basilosaurus cetoides) by the form of the teeth. ^ 

 His remarks on this point are as follows : — " The straight, high, and 

 pointed accessoiy cusps, which are very large as compared Avith the 

 principal cusp, suffice to distinguish the tooth-crowns of Dorudon serra- 

 tus from those of the Zeuglodons from Alabama ; in addition, the roots, 

 both branches of which are always nearly parallel in the latter, in Doru- 

 don diverge at an angle of about 80° . . . Whether one proceeds more 

 properly in keeping Zeuglodon and Dorudon separate as genera, or in 

 treating D. serratus as a separate species of Zeuglodon, is uncertain. I 

 should incline to the first course." 



In the following pages I shall endeavor to explain my own view, which 

 nearly coincides with that of Dames, and is that the genus Dorudon is 

 distinct from Basilosaurus, and that the species which Miiller mentioned 

 as a small form of his hrachyspondylus ^ is allied to the former but repi'e- 

 sents a distinct genus. 



It is somewhat remarkable that Gibbes did not mention more than 

 a part of the specimens which were sent me from the Museum of Com- 

 parative Zoology as belonging to the " Gibbes collection." One can only 



1 Pal. Abh., 1894, (2), Bd. 1, Heft 5, p. 16. He also corrects the erroneous 

 statement of Zittell (Handbuch Pal. Vert., 1893, p. 168) that Dorudon is based on 

 vertebrae of Z. hrachyspondylus. 



2 The confusion between the large form of zeuglodont with short lumbar ver- 

 tebrae and the small form of zeuglodont with short lumbar vertebrae in Miiller's 

 work is very puzzling. The latter is sometimes referred to by him merely as Z. 

 hrachyspondylus, and sometimes as " der kleine Zeuglodon." He was in doubt as 

 to this small form, as shown by his remark on p. 29 : " Whether the small Zeuglo- 

 don is a separate species ... or the young of Ziiglodon hrachyspondylus is still un- 

 certain at present." 



In the appendix to his work (p. 31), however, he describes the small skull now in 

 the Teyler Museum, Haarlem, as " a small individual of Zeuglodon hrachyspondylus." 

 This would be satisfactory if it were not that he also describes the large, short 

 lumbar vertebrae on page 26 under the same name. 



Recognizing this dLfficulty, Von Stromer in 1903 (Mitth. Pal. und Geol. Inst. 

 Univ. Wien, 15, p. 85), limits the name hrachyspondylus to the form represented 

 by large, short lumbars, and assigns the name hrachyspondylus minor to the small 

 species with short lumbars. This nomenclature is accepted in the present paper. 



