1890.] | The Cetacea. 603 
The posterior molars two-rooted; ^ Squalodon Gratel. 
Some of the oix Eae superior molars three- 
rooted ; Trirhizodon Cope. 
E rual grateloupü Pedroni and S. antverpiensis Van Ben. are 
the most abundant European species. In America the S. at- 
lanticus Leidy has been found in New Jersey and Maryland, and 
the S. kolmesti Leidy, a species with more delicate teeth than the 
last, has been discovered in South Carolina. 
vertebræ, tw HEEE E 
FIG. 1. d 
size; a, from below ; 2, lumbar from side ; ¢, cervical from front. Type; original; pun 
Miocene of Maryland. 
The greater number of the PLATANISTIDE are extinct. The 
genera differ much among themselves in the number and form of 
the teeth, and the relative form of the neck. Some of the species 
reach the size of the smaller whales, as the Cetophis heteroclitus 
Cope; but most of the species have the average dimensions of 
the dolphins. The genera differ as follows: 
I. Teeth with roots extended transversely. 
Teeth with lateral basal lobes; lumbar diapophy- 
ses wide; Inia Geoffr. 
