490 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
beaked whales one finds rudimentary denticles which remain in the 
gums and are not cut. 
In this series also we know the most important transitional forms. 
Fig. 19 shows the under jaw of a beaked whale from the Miocene of 
France, Cetorhynchus, 1 which the alveolar groove is greatly reduced 
Fic. 19.—Fragment of the mandible of a Beaked whale, Cetorhynchus christoli Gervais, 
from the Miocene of Poussan, southern France. 3% natural size. 
and the septa between the alveoli have disappeared. ‘The series is 
developed in the same line as the sperm whales, and the transforma- 
tion is similarly nearly completed in the Upper Miocene. At this 
time a genus of beaked whales, J/esoplodon, appears, which is met 
with abundantly in fossil form, but very seldom at the present day. 
Fic. 20.—Skull of a Sperm whale, Physeter macrocephalus L. Length of the body reaches 
18 meters (59 feet). After W. H. Flower. The mandible has 27 large single-rooted 
teeth on each side; the upper jaw and the premaxille which form the end of the snout 
are toothless. 
Still another independent series springs from the squalodons, 
which has its highest development in the Miocene, but at the present 
time is on the decline. To this group belong the small South Ameri- 
ean river dolphins (Stenodelphis and Inia) and the white whale and 
narwhal. 
