292 MARSUPIALIA. 



Leptocladus dubius, Owen l . 



This is the type species. 

 Hob. Europe (England). 



47739. Part of the left ramus of the mandible, containing eight 

 (Fig.) cheek-teeth, of which the four first are probably premolars ; 

 from the Middle Purbeck group of Durdlestone Bay, 

 Swanage, Dorsetshire. This specimen is the type, and is 

 figured by Owen in his ' Mesozoic Mammalia ' (Mon. Pal. 

 Soc.), pi. iii. fig. 4. Beckles Collection. Purchased, 1876. 



Family SPALACOTHERIID^l. 



Dentition (in type genus) : 1. \, C. \, Pm. + M. ^. The lower 

 true molars of the type genus closely resemble in structure those of 

 Chrysochloris, consisting of a single column surmounted by three 

 cusps arranged in a V. The upper true molars described under the 

 name of Peralestes likewise agree with those of the same genus. 

 The lower true molars decrease in size posteriorly. Marsh 2 refers 

 the American Jurassic genus Menacodon to this family. 



Genus SPALACOTHERIUM, Owen 3 . 



The characters of this genus are the same as those of the family. 

 The so-called Peralestes (in which there are six upper true molars) 

 is probably founded upon the upper jaw of the present genus. 



Spalacotherium tricuspidens, Owen '. 

 This is the type species. 

 Hob. Europe (England). 



46019. Fragment of the hinder part of the left ramus of the man- 

 dible, showing the last four true molars, together with 

 the impress in the matrix of the anterior portion of the 

 ramus ; from the Middle Purbeck group of Durdlestone 

 Bay, Swanage, Dorsetshire. This specimen (woodcut 

 fig. 43) is the type, and is figured by Owen in the ' Quart. 

 Journ. Geol. Soc.' vol. x. p. 426, fig. 1, and also in his 

 ' Mesozoic Mammalia ' (Mon. Pal. Soc.), pi. i. fig. 32. 



Purchased, 1874. 



1 Mesozoic Mammalia (Mon. Pal. Soc.), p. 53 (1871). 



2 Amer. Journ. ser. 3, vol. xxxiii. p. 340 (1887). 



3 Quart. Journ. Geol. Soc. vol. x. p. 426 (1854). 4 Loc. cit. 



