HISTORY OF MARINE MAMMALS—ABEL. 487 
These squalodons approach the primitive cetaceans of the Eocene in 
the form of the posterior teeth, and as in the latter these teeth in 
some species are three-rooted. An important difference exists, how- 
ever, in the number of the teeth. While the primitive cetaceans 
have only 11 teeth on each side of the upper and lower jaws, in the 
squalodons the number is 14 or 16. The simplification of the teeth 
proceeds so far that the incisors, canines, and many of the anterior 
premolars are of the same form. 
The skull of the squalodons reminds one strongly of that of exist- 
ing toothed whales. The nostrils are pushed far back in the skull, an 
adaptation for breathing in the water. With the squalodons begins 
an almost unbroken series which leads to the existing sperm whale. 
Fic. 15.—Skulls of two squalodont cetaceans, Squalodon. A Squalodon zitteli Paquier, 
from the Miocene of Bleichenbach in Lower Bavaria. } natural size, After K. A. 
von Zittel. B. Squalodon bariensis Jourdan, from the Miocene of Bari in southern 
France. 5 natural size. After Lortet. 
Between 1861 and 1863, when the fortifications of Antwerp were 
built, thousands of whale skeletons were dug up, and among them 
forms which show in the clearest manner how the transition between 
the squalodons and the sperm whale has taken place. 
First we see that in the different forms of Scaldicetus (fig. 16) the 
two-rooted teeth have become single-rooted through the fusing to- 
gether of the roots. The crowns of the teeth, which were originally 
compressed, have become conical. The cusps on the edges of the 
teeth have disappeared and resolved themselves into fine serrations, 
whose remains finally are only indistinctly seen on the crowns of the 
teeth. The crowns are shorter and the roots longer and thicker. 
The teeth stand obliquely and form a formidable grasping appa- 
ratus. 
41780—08 ‘ 
x 
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