TRICONODON. 351 



tougli chitinous cases and elytra of insects. The particular 

 modification of the pointed cusps, as to number, proportion, 

 and relative position, resembles in some degree that of the 

 Cape mole {Ghrysochlora awrea), but both in these respects 

 and in the number of molars, the dentition accords more 

 closely with that of the extinct Amphitherium. The chief 

 interest in the discovery of the SpalacotJierium is derived 

 from its demonstration of the existence of Mammalia about 

 midway between the older oolitic and the oldest tertiary 

 periods. 



Both the Oxford oolitic slate and the Purbeck marly shell- 

 beds give evidence of insect life ; in the latter formation abun- 

 dantly. The association of these delicate Invertebrata with 

 remains of plants allied to Zamia and Cycas, is indicative of 

 the same close interdependency between the insect class and 

 the vegetable kingdom, of which our power of surveying the 

 phenomena of life on the present surface of the earth enables 

 us to recognize so many beautiful examples. Amongst the 

 enemies of the insect class ordained to maintain its due nume- 

 rical relations, and organized to pursue and secure its count- 

 less and diversified members in the air, in the waters, on the 

 earth and beneath its surface, bats, lizards, shrews, and moles 

 now carry on their petty warfare simultaneously, and in 

 warmer latitudes work together, or in the same localities, in 

 their allotted task. ~No surprise need therefore be felt at the 

 discovery that Mammals and Lizards co-operated simultan- 

 eously and in the same locality at the same task of restraining 

 the undue increase of insect life during the period of the de- 

 position of the Lower Purbeck beds. 



Genus Triconodon, Ow. 



Sp. Triconodon mordax. — This name is proposed for a small 

 zoophagous Mammal, whose generic distinction is shewn by 

 the shape of the crowns of the molar teeth of the lower jaw, 

 (fig. 1 1 8), which consist of three nearly equal cones on the same 



