59 



The species of this genus are but imperfectly determined, and much 

 confusion in regard to their number exists among the comparative 

 anatomists of the present day. Professor Owen treats only of two 

 species, the Z. macrospondylus and the Z. cetoides? to which M. Pictet 

 and several others add the Z. hydrarclius? Carus, Z. trachyspondylus? 

 Miiller, and the Z. Qiblesii ? (Dorydon 4 of Gibbes.) 



Of these, the Z. Cetoides appears to be the largest, attaining in 

 length to about seventy feet, although M. Koch exhibited a skeleton of 

 one which measured 114 feet long ; this specimen, however, is considered 

 to be made up by connecting the vertebrae of two distinct species, the 

 Z. macrospondylus and Z. trachyspondylus, and consequently the 

 accuracy of the foregoing dimension is now generally ignored. 



The Z. hydrarchus varies from the Z. macrospondylus by possessing 

 in the upper jaw four conical double-rooted teeth between the incisors 

 and molars instead of two and the Z. trachyspondylus is likewise dis- 

 tinguished from it by the rough and shorter formed vertebrae of the 

 spinal column. 



Genus SQTTALODON, Grateloup. 



The very imperfect remains of only an upper jaw yet found leave 

 the question still doubtful whether this extinct species ought to be con- 

 sidered as a reptile or a cetacean. M. Grateloup, the originator of the 

 genus, places it among the former ; while M. Beneden, Pedroni, and 

 Agassiz assert its affinity to the latter. The number of teeth shown by 

 these fragments amounts to at least i^, for the tip of the beak is muti- 

 lated; and incisors, known but by the alveoli, canines and molars, are 

 distinctly exhibited, not doubtfully, as in the Zeuglodon. The molars 

 are similar in their crowns to those of the Zeuglodon, but some of them 

 are three-rooted. Until determined by better specimens, the Squalodon 

 will have to occupy its present position. 



SQUALODON GBATELOTJPII, Gervais. 

 Squalodon grateloupii, Gervais. 

 Delphinioides grateloupii, Pedroni. 

 Phocodon (?), Agassiz. 



Teeth S (?)> large, compressed, double or treble rooted ; muzzle 

 not well known, elongated. 



Discovered in the tertiary deposits in France and Austria. 



1 KTJTOS, whale whale-like. 



2 u'Spa, sea-serpent, and &px os > original, primitive. 



3 rpaxts rough, and o-TrovSuAos, dorsal vertebrae. 



4 S6pv, a spear, and 65ovs, tooth. 



