TRIPLOPUS. . 681 



The sympliysis is quite contracted and is short. The mental foramen is 

 below the middle of the inferior diastema. The ramus is compressed and 

 -at the same time strong. 



Deniition. — As the deciduous third and fourth premolar teeth, in a worn 

 condition, remained in the maxillary bone, I removed them from one side, 

 thus displaying the crowns of the coiresponding permanent teeth. The 

 first premolar may belong to the permanent dentition; the second is the 

 deciduous. The former has two roots. The crown is cutting for a short 

 distance anteriorly, but posteriorly it expands into a heel, much less de- 

 veloped than the internal lobe of the succeeding teeth The crowns of the 

 third and fourth premolars differ externally, as well as in their crests, from 

 those of the true molars. The median-anterior and cingular vertical ridges 

 are not so prominent as in the latter. The external crest is not divided 

 into two by the notch in its grinding face. The anterior cross-crest, at its 

 inner or distal extremity, is turned shortly backwards and then inwards, 

 giving a "pot-hook" outline to the triturating surface. The fourth decid- 

 uous premolar presents a peculiar character already ascribed to the first 

 true molar. This consists of a crest running parallel with the posterior 

 transverse crest and close to it, along its posterior side It forms the liorder 

 of the tooth for a short distance, but as its direction is slightly obliquely 

 forwards as well as outwards, the posterior cingulum appears for a very 

 short distance. 



The first true molar is subquadrate in outline. The anterior trans- 

 averse crest commences at the middle anterior ridge, and is first transverse, 

 then directed a little obliquely backwards. The second crest commences 

 at the apex of the posterior external crescent, leaving a wide posterior 

 marginal fossa. Its internal extremity is broken off. Posterior to, and in 

 contact \yith it, the posterior cingulum rises in a crest, which occupies the 

 internal half only of the border. Its inner border is imperiect. It appears 

 to me to be probable that the normal posterior crest is turned posteriorly 

 on itself so as to give the "pot-hook" shape seen in the anterior crest of the 

 fourth permanent premolar. The corresponding accessory crest in the 

 fourth temjDorary premolar appears to have been distinct at its internal ex- 

 tremity. The second true molar has a more oblique posterior external 

 crest, and the posterior internal is oblique and simple. It has narrow ante- 



