﻿2<S2 Allen's naturalist's library. 



molar teeth carrying two or three longitudinal ridges support- 

 ing numerous small tubercles, such ridges being separated by 

 deep grooves, as shown in the accompanying figures, and the 

 number of ridges in the upper molars being usually one in 

 excess of those of the corresponding lower teeth. As in the 

 Diprotodont Marsupials, there is a single pair of large and 

 sharp incisor teeth in the lower jaw ; and a further superficial 

 resemblance to that group is often shown by the last premolar 

 being modified into a large compressed and cutting tooth with 

 well-defined parallel groovings and ridges on the sides of its 

 crown. 



The numerous genera of the Multituberculata are arranged 

 under several families, which will form the headings under 

 which our brief remarks will be arranged. 



FAMILY TRITYLODONTID^. 



GENUS TRITYLODON. 



Tritylodoji, Owen, Quart. Journ. Geol. Soc, vol. xl., p. i+6 

 (1884); Lydekker, Cat. Foss. Mamm. Brit. Mus., pt. v., 

 p. 201 (1887). 



In this family the upper molar teeth have three longitudinal 

 ridges, as shown in the last illustration, and are broader 

 than long ; while the premolars are of the same general struc- 

 ture, but somewhat simpler. In the upper jaw there is one 

 pair of large, somewhat chisel-like incisors, followed by a 

 second very small and functional pair ; then, owing to the 

 absence of a canine, comes a very long gap, followed by the 

 two premolars, and these again, by the four molars. The lower 

 jaw is unknown. 



This genus is typically represented by T. longcBvus, from the 

 Secondary rocks of South Africa, which was an annual of the 



