THE TRUE DOLPHIN. 59 



capsule is eventually obliterated. Then another 

 event occurs; ossification of the jaws takes place 

 within the alveoles, and as the teeth are not opposed 

 to each other, and no force retains them in their 

 places, they are soon thrust out and disappear. This 

 explains the very variable number of teeth we find 

 in dolphins of the same species, and still more so 

 in those of different species. Thus, not having ob- 

 served between the teeth of dolphins any essential 

 difference of form, and their differences of number 

 not being determinate, we have nothing but the 

 form of their heads from which to establish the 

 generic differences. 



Species I. — The true Dolphin.* 



Delphinus Delphis; L. 



Le Dauphin: Bonnaterre; Cetol. 20, pi. x, fig. 2. 

 Dauphin Vulgaire: Desm. Mammal, sp. 758, p. 514. 



[Called Grampus, Porpess, Herring hog, Dolphin.] 



Hitherto the subjects of our study have been 

 inhabitants of grassy plains, or shady forests; the 

 margins of gentle streams, or the outlets of mighty 



$ We call this the true Dolphin to distinguish it from the 

 fish called dolphin by sailors, (the corypheena purpuris) and 

 because this species is the dolphin so celebrated in various 

 ancient poems and fables, to which we shall hereafter refer. 



