952 



wrinkles ; lower incisor with root extending slightly beyond 

 m 3 , which is deflected outward to allow its passage ; section 

 of shaft much as in upper tooth but antero-posterior diameter 

 relatively greater and inner border more flattened. Cheek- 

 teeth large, their roots forming conspicuous capsule-like pro- 

 jections in orbit, and low but evident protuberances on lower 

 portion of outer side of lower jaw, both upper and lower root 

 capsules becoming less noticeable with advancing age ; outline 

 of crowns squarish, tending to be broader than long above, 

 longer than broad in the mandibular teeth, the outer border of 

 upper teeth and inner border of lower teeth straight, slightly 



crenulate, the opposite borders dis- 

 tinctly bilobed. The pattern of 

 enamel folding is essentially the 

 same in all the teeth : three narrow 

 re-entrant folds on one side, a single 

 wider fold on the other ; in the 

 maxillary teeth the three folds are 

 on the outer side, while in the 

 mandibular teeth they are on the 

 inner side ; inner fold in maxillary 

 teeth nearly straight, extending 

 obliquely forward to come in con- 

 tact with extremity of first outer 

 fold, or frequently in pm 4 to curve 

 slightly behind it ; outer fold in 

 mandibular teeth curving backward 

 between extremities of second and 

 third inner folds, with both of which 

 it is nearly or quite in contact. In 

 the maxillary teeth the first outer fold extends obliquely forward 

 half-way across crown, or in pm 4 occasionally about to inner 

 border, the second outer fold curves noticeably backward and 

 extends nearly to inner side of crown, and the third outer fold 

 extends directly inward or somewhat obliquely backward, its 

 length equal to or a little less than that of first fold, except 

 when the latter assumes its lengthened form. In the mandi- 

 bular teeth the first and third inner folds extend nearly across 

 crown, while the second is often distinctly shorter, all three are 

 somewhat wavy in outline, the first the least so. 



Measurements. — Adult female from the Rhone, near Aries, 

 France : head and body about 820 ; tail about 380 ; bare portion 

 of tail (in dry specimen), 310 X 120 ; hind foot, 170; ear, 35. 

 Immature male from the same region : head and body about 650 ; 

 tail about 250 ; bare portion of tail (in dry specimen), 225 x 110 ; 

 hind foot, 160. For cranial measurements see Table opposite 



Fig. 198. 



Castor fiber. Cheek-teeth. 

 X 11. 



Specimens examined. — Six, from the following localities : 

 Noeway: Froland, Kristiansand, 1. 

 England: Norfolk, 1 (skull). 



