INSECTIVORES. 419 



of the teeth become anchylosed to the jaw-bone, — a reptilian character 

 offered by the Soricida alone in the Mammalian Class. 



163. Erinaceidcs. — In the dentition of the Tupaiaa (Glisorex) we 

 begin to trace characters intermediate between those of the dentition 

 of Shrews and of Hedgehogs. The dental formula of the Glisorex 

 tana is: in. IeI, c. Je^, pm. f^J, m.~:=36: the upper incisors are 

 small, simple, and wide apart in the upper jaw(l) ; the anterior incisor 

 in the lower jaw is long and procumbent, but relatively smaller than 

 in the Shrews ; the canines are small in both jaws ; the premolars 

 increase in size and complexity as they approach the true molars ; 

 the first two of these are sub- equal with six cusps in the upper and 

 five cusps in the lower jaw, the last true molar is smaller and is 

 tricuspid. 



In Macroscelis (Elephant-mice of the Cape) and Gymnura each 

 intermaxillary bone contains three teeth, which, in the former genus 

 are succeeded by four premolars and three true molars, with the 

 same number of teeth in the lower jaw. In Gymnura{2) the first tooth 

 which succeeds the incisors has the form and size of a canine in both 

 upper and lower jaws ; this is followed by four premolars, the last 

 of which in the upper jaw is large and quadri-cuspid like the first 

 and second of the true molars, which have square crowns : the last 

 true molar is smaller and triangular. In the lower jaw of the 

 Gymnura the fourth premolar has a compressed tri-cuspid crown. The 

 dental formula of Gymnura is : in. 3^, c. }Ei, pm. 4=5, m. |^: = 42. 



The dentition of our common Hedgehog {Erinaceus euro- 

 pcBUs) shows greater inequality in the upper and lower jaws, the 

 formula being : — in. ~, pm. |e|, m. ^, = 36.(3) The first in- 

 cisor in both upper and lower jaws is larger and longer than 

 the rest, and is very deeply implanted in the jaw : the tooth 

 which follows the incisors is small in both jaws, but especially 

 so in the lower, and it does not merit a distinction from the other 

 premolars : the last premolar is the largest in both jaws ; above, it 

 has a quadricuspid crown with three fangs ; below, a subcompressed 

 tricuspid crown with two fangs. The true molars decrease in size 

 from the first to the third in both jaws : the first and second have 



(1) PI. Ill, fig. 3. (2) PI. 111. fig. 4, 4a, 4&. (3) PI. 110, fig. 5, 



E E 2 



