286 



ANATOMY OF VERTEBRATES. 



222 



The upper true 

 have triangular 



the exterior part of the crown is raised into one large pointed 

 middle cusp and two smaller cusps ; a small strong obtuse lobe 

 projects from the inner side. The molars of the lower jaw are 

 compressed and tricuspidate ; the middle cusp being the longest, 

 especially in the two last molars, which resemble the feline car- 

 nassials. 



The dental formula of the genus Dasyurus is 



i*A. c l.*A. m *A = & fiff 229 



O Q * 1 1 y J: O O ' A A ~~~ ? & ^^^' 



The eight incisors of the upper jaw, fig. 222, are of the same 

 length and simple structure, and are arranged in a regular semi- 

 circle. The premolars, p 2 and 

 3, answer to the two last in 

 Thylacinus, and have simple 

 crowns, 

 molars, m 



crowns ; the first presents four 

 sharp cusps ; the second and 

 third each five ; the fourth, 

 which is the smallest, only 

 three. In the lower jaw, the 

 last molar is nearly of equal 

 size with the penultimate one, and is bristled with four cusps, the 

 external one being the longest. The second and third molars 

 have five cusps, three on the inner and two on the outer side ; the 

 first molar has four cusps. The carnivorous character of the 

 above dentition is most strongly marked in the Ursine Dasyure, 

 or Devil of the Tasmanian colonists, the largest existing species 

 of the genus. 



In some of the smaller species the canines lose their great rela- 

 tive size, and the molars present a surface more cuspidated than 



sectorial ; there is also an increased number 

 of teeth, and as a consequence of their 

 equable development, they have fewer and 

 shorter interspaces. The subgenus Phasco- 

 gale is characterised by 



Dentition of Ursine Dasyure. 



.4.4 



LI 



3.3 



4.4 



m 



- 46, fig. 223. 



Dentition of Phascogale. 



1 3.3' "1.1 ; ^3.3' "4.4 



In this formula may be discerned a step in 

 the transition from the Dasyures to the Opossums, not only in 

 the increased number of spurious molars, but also in the shape 

 and proportions of the incisors. 



The general character of the dentition of these small predatory 



