230 



MEMOIRS OF THE UNIVERSITY OP CALIFORNIA. 



indication of an anterior basal tubercle occurs less frequently and is less dis- 

 tinct than in the Alaskan wolves. A faint posterior basal tubercle is present 

 in some instances. Ordinarily both anterior and posterior basal tubercles are 

 absent. 



P 2 in most cases shows no trace of either anterior or posterior tubercles, the 

 tooth being as simple in form as the anterior lower premolars of Temnocyon. 

 In a few cases, as in specimen 10727 (fig. 7), a well-developed posterior basal 

 cusp is present with a minute posterior basal tubercle situated behind it. 



P 3 possesses a distinct posterior cusp, and a minute posterior basal tubercle 

 is sometimes present. The posterior shelf or heel of the cingulum may be prom- 

 inent and rather sharply turned up on the posterior side, as in the modern 



wolves ; or may, as in no. 10856, be much less 

 distinctly marked, and may slope downward 

 from the posterior basal cusp to the poster- 

 ior margin of the tooth without exhibiting 

 any upward curvature. 



P 4 is relatively large compared with P :! , 

 but shows almost exactly the same size in 

 relation to Mi as is seen in the Alaskan C. 

 pambasileiis. The posterior cusp and pos- 

 terior basal tubercle are well developed. 

 The posterior portion of the tooth is some- 

 what wider than the anterior in many cases. 

 The posterior basal tubercle is usually situ- 

 ated on the extreme posterior portion of the 

 cingulum, and its posterior border is the 

 extreme posterior margin of the tooth. In some cases, as in no. 10727, this 

 tubercle is separated from the posterior border by a distinct notch and another 

 small tubercle is present on the posterior margin of the cingulum. 



In M 1 , the trigonid portion of the tooth is generally relatively long and mas- 

 sive, or the heel region is relatively short compared with the large Recent wolves 

 of North America. The metaconid is also generally smaller than in the 

 modern species, though not always smaller than in all the Recent varieties. 

 The hypoconid portion of the heel exhibits a tendency toward relatively greater 

 development than the entoconid region. In nearly all specimens three small 

 tubercles have developed in the space between the metaconid and the entoconid. 

 One of these is usually situated on the base of the metaconid, one on the base 

 of the entoconid, and one intermediate between the two. In some cases the 

 number of these secondary tubercles varies above or below three, and their 

 position may also vary somewhat from the situations indicated as most typical. 

 M 2 and M 3 , the tubercular molars, are relatively small both anteroposterioiiy 



Figs. 6 and 7. Canis dirus Leidy. Lateral 

 view of inferior premolar series. Fig. 6, 

 no. 10834, natural size; fig. 7, no. 10727, 

 natural size. Bancho La Brea Beds. 



