TRICONODON 317 



the last of the series. The sharp multicuspid character of so 

 much of the dental series as is here preserved, repeats the 

 general condition of the molar teeth of the small insectivorous 

 Mammalia in a striking degree : one sees the same perfect 

 adaptation for piercing and crushing the tough 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 {GhrysocJilora 

 atirea), but both in these respects and in the number of molars, 

 the dentition accords more closely with that of the extinct 

 Amphithcrium. The chief interest in the discovery of the 

 Sfialacotherium is derived from its demonstration of the exis- 

 tence 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 Gycas, 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 

 numerous enemies of the insect class ordained to maintain its 

 due numerical relations, and organized to pursue and secure 

 its countless 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. 



