1883] On the Extinct Dogs of North America. 247 
there is a cutting heel. The number of true molars, }, is the 
smallest in the family. A single species is known, the O. crassi- 
vultus Cope, from the John Day bed of Oregon. The skull is 
about the size of that of the wolverene (Gulo luscus), and is of 
robust form. The canine teeth are powerfully developed, and in- 
dicate an animal of strong predaceous instincts. 
GENERAL OBSERVATIONS. 
The succession of these genera, as indicated by their structure, 
is as follows: 
Dysodus Icticyon Hyzenocyon 
Elurodon \ Oligobunis eanyarseren 
; rf et 
: Canis Fy cshesrcet 
Galcconiis 
Marna 
Mepalotis 
This order is not entirely that of succession in time. Thus 
Megalotis, which represents the primitive type of all Canidae, is 
only known as living, and the Mega/otis zerda is African. We 
anticipate its discovery in a fossil state. Amphicyon and Ga- 
__lecynus are the oldest known Canidz, as they characterize the 
lowest Miocene, and probably the Upper Eocene epochs, Canis 
appears next in time in Europe, probably in the Middle Miocene. 
In America the genera of the John Day Middle Miocene pre- 
cede Canis. I refer to Temnocyon, Enhydrocyon, Hyznocyon 
and Oligobunis, which were contemporaries. Ælurodon appeared 
later than Canis in the Upper Miocene and Loup Fork, and Dy- 
_ Sodus and Icticyon with various other genera not here enumerated, 
_ are recent. Canis is the prevalent genus in the present period, as 
‘ Galecynus was during the Miocenes. That the last named genus, 
Za its numerous species, has given origin to the existing spe- 
_ “es of Canis, as suggested by Filhol, is altogether probable. 
a As already mentioned, the successional change in the Canidz 
“2 has been exhibited in the reduction of the numbers of the tuber- 
T cular teeth, To this may be added a successive increase in the 
Size of the Sectorials and canines. In these points the Canidze 
