xxvi INTRODUCTION. 



teeth in each jaw have each a crown consisting of one median and two 

 small lateral lobes ; but in either outermost incisor the inner lobe is 

 obsolete. In the upper jaw the first premolar has but a single fang. 

 All the teeth behind it have two fangs each, while the last three upper 

 teeth have each three. In the lower jaw the first premolar and the third 

 molar have each only one fang, while all the intermediate teeth have 

 two fangs. 



The upper sectorial tooth has a very large anterior external cusp, 

 the apex of which is directed backwards as well as downwards, 

 while on its inner side is a very small antero-internal cusp. A second, 

 broad, external cusp is placed behind the anterior one, but does not 

 extend so far downwards. In the Felidte, however, there are three 

 external cusps, whereof the most anterior is obsolete in the Dog. 



The first upper true molar has a very extensive grin ding-surface, 

 with two large external cusps, two smaller internal ones, with also 

 a very large internal band of tooth-substance or " cingulum." The 



v O 



second upper true molar is formed like the first, but is only about 

 half its size. 



The first lower premolar consists of one conspicuous cusp with a 

 rudimentary one behind it. The next three teeth have each a large 

 anterior cusp with two small ones behind it, whereof the anterior is the 

 larger and more elevated. 



The lower sectorial tooth consists of a large anterior cusp, followed 

 by one still larger (whereas in the FeHdte they are of nearly equal size), 

 with a minute cusp postero-internal to it. These last two cusps play 

 against the inner surface of the two large cusps of the upper sectorial. 

 Behind the three cusps just described, the lower sectorial possesses a 

 very large posterior prolongation, or "talon," which bears two cusps, 

 whereof the external one is the larger. The surface of the talon bites 

 against that of the anterior, upper true molar. 



The second true molar of the mandible has a quadrate grinding- 

 surface with two transverse ridges, the anterior one being divided into 

 two subequal cusps. The third true molar is very small with a rounded 

 crown. 



Each milk-molar resembjes, not the tooth which replaces it, but the 



