206 NORTH AMERICAN MUSTELIDiE. 



less of a girdle, and scarcely an anterior heel. The anterior pre- 

 molar is like the last, but smaller still, and single-rooted. I 

 have not seen its abortion. In very old skulls, the two molars 

 become ground almost perfectly flat, and the premolars become 

 stubby cones. The lower canines are shorter, relatively stouter, 

 and more curved than the upper ones ; there is usually quite 

 an elbow at the point of greatest curve. The inferior incisors 

 are more nearly of a size than is usual in Musteliiue^ and more 

 regular, i. e., none are crowded out of the general plane j but 

 this is a matter of degree only. The outer pair is larger than 

 the rest ; viewed from the front, they widen from base to tip, 

 and the apex is emarginate. The next pair sets a little back 

 from the general plane ; for, though their faces are generally 

 quite flush with the others, yet their greater thickness causes 

 them to protrude behind. All the under incisors are approxi- 

 mately of one length. The cutting edge of the outer pair is 

 oblique; of the others, horizontal. The cutting edge of the 

 outer pair is nicked, as already said, and the front faces of the 

 rest are marked by a sulcus ending in a slight bilobation of their 

 cutting edges. 



Variation in the skull with special reference to geographical distri- 

 bution. 



Having already called attention to this matter in a general 

 way, I cannot do better than continue the subject with Mr. J. 

 A. Allen's tables of measurements and critical comment, which 

 set forth the subject in more precise detail :* — 



" The twent^^-nine skulls of this species of which measure- 

 ments are given below show a wide range of variation in size, 

 and a decided decrease southward. The localities embrace such 

 distant points as California and the Atlantic seaboard on the 

 one hand, and Maine and Texas on the other ; but, with one or 

 two exceptions, the specimens from any single locality are un- 

 satisfactorily few. The specimens range in length from 2.60 to 

 3.50, and in width from 1.60 to 2.25 ! Yet there is not a speci- 

 men included in the series that is not so old as to have all the 

 cranial sutures obliterated. A portion of the difference is doubt- 

 less sexual, but the specimens, unfortunately, have not the sex 

 indicated. Ten of the specimens may be considered as western, 

 coming mainly from Utah and California ; ten others are from 



* Bull. U. S. Geol. and Geog. Surv. Terr. vol. ii. no. 4, 1876, pp. 332-334. 



