TEETH OF DIPHYODONTS. 



307 



cular incisive series, as in ruminants, and is separated by a slight 

 interval from the premolar, 2. The canine above, A, c, has a long 

 compressed pointed crown, with a sharp hind border : its root is 

 deeply implanted and divided into two fangs : it descends outside 

 the lower teeth and their alveoli, reminding one of the canines in 

 the small Musk-deer. The upper premolars, A, p, 2, 3, 4, have 

 compressed pointed crowns increasing in size as they approach 

 the molars : the hind border of the second has one notch, that of 

 the third two notches, and a low sub-bilobed inner portion. The 

 molars decrease in size to the third : the first and second above 

 have two outer cusps more produced than the two inner ones : 

 the third molar has the hind pair blended into one cusp. The 

 first lower premolar has a longer but thinner crown than the 

 last. The first and second lower molars are 4-cuspid ; the third, 

 3-cuspid ; and the first has an anterior talon. 



Macroscelides and Pctrodromus, also South African Insec- 

 tivora with long hind-limbs and a long snout, have similar 

 4-cuspid molar teeth, the last molar the smallest and with the 

 outer and inner cusps of the hind pair blended into one. The 

 last premolar above has a low beginning of the inner cusps, 

 which are the lowest in the true 

 molars. In the lower jaw of 

 Macroscelides fuscus the type 

 series is preserved, viz. : i 3, 

 c i , p 4, m 3 ; but p \ is undeve- 

 loped above; and p \ is wanting, 

 both above and below, in Pe- 

 trodromus, as in Rhynchocyon. 



Bdeof/ale crassicauda (Pe- 

 ters), with the following for- 

 mula : 



24.3 



o o 11 



. O .O I.I 



-/ 



3.3' 1.1 ' 



3.3 3.3 



m - - = 40, 



3.3' "3.3 



is remarkable for the large pro- 

 portional size of the upper 

 outer incisor, which almost 

 equals the canine. 



In the dentition of the Tu- 

 paias (Glisorex, fig. 243) we 

 trace characters intermediate 

 between those of Shrews and Hedgehogs. The dental formula of 

 Glisorex tana is- 



.2.2 1.1 3.3 3.3 



P .TO 5 o-o = 36 - 



Dentition of Tupain. 



1. Upper jaw, b side view, working surface 



2. Lower jaw, a working surface, b side view. 



2.2' '1.1' 



3.3 

 x 2 



3.3 



