Genera of Felida? and Canida?. 97 



of the third and fourth premolars, as well as a low posterior 

 heel and a rudiment of an anterior one. The heel of the 

 sectorial is shorter than the remaining part of the tooth, and 

 rises to a cutting-edge a little external to the middle line ; 

 there is a small tubercle at its interior base. The anterior 

 blade-cusp of the sectorial is much lower than the median, 

 which is conical ; the two diverge, diminishing the shear-like 

 character and action of the tooth ; the internal cusp is well 

 developed. The first tubercular is of moderate size, and is a 

 longitudinal oval in outline ; the crown supports two low 

 tubercles anterior to the middle, of which the external is the 

 larger. The last molar has a single compressed root ; and the 

 crown is a longitudinal oval in outline : its position is on 

 the ascending base of the coronoid ramus ; so that the crown 

 is slightly oblique. The masseteric fossa is profound and 

 well defined ; its anterior termination is below the middle of 

 the second tubercular tooth. The horizontal ramus is not 

 robust, but is compressed and rather deep. 



Measurements of Mandible. 



metre. 



Length along bases of posterior five molars -049 



Length of base of fourth premolar -Oil 



Elevation of crown -008 



Length of base of sectorial -018 



Elevation of crown of sectorial -01 2 



Length of base of first tubercular '0075 



"Width of base of first tubercular -005 



Length of base of second tubercular -005 



While the characters of this dog do not separate it widely 

 from the genus Cams, many of them are quite different from 

 those presented by the recent species of the genus with which 

 I am acquainted. Thus the union of the foramina spheno- 

 orbitale, rotundum, and alisphenoidale anterius, the anterior 

 position of the orbits, and the postorbital constriction are not 

 seen in the wolf, domestic dog, coyote, jackal, or the North- 

 American and European foxes. The size of the brain was 

 evidently less than in those species, and the sectorial teeth 

 quite inferior in the efficiency of their blades. These characters 

 may be considered in connexion with the low geological posi- 

 tion of the beds in which the species occurs. 



From the Truckee beds of the White-Eiver formation in 

 Oregon. 



Canis, Linn. 



The names proposed by Smith, Gray, and others, and 

 which must be regarded as synonyms of Canis, are Ltipus, 

 Dieba, Simenia, Chrysocyon, and Lycalopex. Many of the 



