302 PALEONTOLOGY 



gardt, the geological relations of which are well determined as 



between lias and Kenper sandstone. The teeth of Microlestes 

 from Frome, submitted to the writer by the discoverer, Mr. 

 Charles Moore, F.G.S., in 1858, are four in number, two being 

 molars of the upper jaw, each with four fangs ; one a molar 

 with a narrower crown and two fangs from the lower jaw ; and 

 the fourth a small, pointed, front tooth. The crowns of the 

 molars are short vertically in proportion to their breadth ; the 

 distinct enamel contrasts with the cement-covered fangs ; the 

 grinding surface shows a wide and shallow depression, sur- 

 rounded by small, low, obtuse cusps, three of equal size being 

 on one side, a larger cusp near one end, and smaller and less 

 regular cusps on the side opposite the three. One lower molar 

 shows a similar type, but with the three marginal cusps less 

 ecpial in size : a second smaller, and from a mure anterior pari 

 of the series has three low cusps on one side, and but one cusp 

 on the other side of the crown, the grinding surface of which 

 presents an elongate triangular form. This tooth had two 

 fangs. The crown of the largest of the upper molars does not 

 exceed one line in its longest diameter. Amongst existing 

 Mammals, some of the small molars of the marsupial and 

 insectivorous Myrmccobius of Australia offer the nearest resem- 

 blance to these fossil teeth ; but a still closer one is presented 

 by the small tubercular molars of the extinct oolitic Mammal 

 called Plagiaulax (fig. 93, m, i and 2). 



Genus Dromatherium. — It would appear that the Mammal 

 from the American triassic or liassic coal-bed (promathcrium 

 sylvestre, Emmons) also found its nearest living analogue in 

 M i/rmccobius ; for each ramus of the lower jaw contained 10 

 small molars in a continuous series, 1 canine, and 3 conical 

 incisors, the latter being divided by short intervals. 



Genus Amphtxhebium ( Thylacotherium, Val.)* — This genus 



* For the full description ami demonstration of tin- mammalian nature of this 

 iiiuch-tli.scu.ssed fossil, sec Owm. History of British Fossil Mammals, 8vo, )>. '-".'. 



