HISTORY OF MARINE MAMMALS—ABEL. 485 
viously only scattering remains of mammals were obtained, namely, in 
the vicinity of Cairo and in the Fayum. 
The oldest whale which we know to-day, Protocetus (fig. 11), differs 
so extraordinarily from living whales that at first sight one could 
hardly assign it to this group of animals. The skull, and particu- 
larly the teeth, show, on the other hand, an astonishing resemblance 
to the oldest land mammals. 
As in the latter, the oldest primitive cetacean has 3 incisors, 1 ca- 
-nine, 4 premolars, and 3 molars on each side of the upper and lower 
jaws. As in the carnivores, the canine projects strongly. The teeth 
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Fic. 13.—Skull of a primitive cetacean, Prozeuglodon atrox Andrews, from the lower 
Middle Eocene of the Fayum (Egypt). Length of skull 60 cm. (23.6 in.). A. From 
the right side. B. From above. After C. W. Andrews. 
which follow it are two-rooted, the posterior three-rooted. The 
edges of the teeth are smooth. The number of teeth in this primitive 
cetacean must have been 44, a great contrast to the recent long- 
beaked dolphin, which has 246 teeth. 
To this primitive form is joined another, ocetus (fig. 12), which 
differs through the fine serration of the edges of the teeth. ‘Then 
follows, also in the same deposits of the Middle Eocene sea, a third 
form, Prozeuglodon. (Fig. 13.) In this cetacean the teeth are not 
formed as in land mammals, but the edges are strongly serrated. 
