224 HISTORICAL PALAEONTOLOGY. 



are now exclusively confined to the Australian province, South 

 America, and the southern portion of North America. In 



Fig. 158. The Banded Ant-eater (Myrmecobius fasciatns) of Australia. 



the Old World, the only known Triassic Mammals belong to 

 the genus Microlestes, and to the probably identical Hypsi- 

 prymnopsis of Professor Boyd Dawkins. The teeth of Micro- 

 lestes (fig. 157) were originally discovered by Plieninger in 

 1847 in the "bone-bed" which is characteristic of the sum- 

 mit of the Rh?etic series both in Britain and on the continent 

 of Europe ; and the known remains indicate two species. In 

 Britain, teeth of Microlestes have been discovered by Mr 

 Charles Moore in deposits of Upper Triassic age, filling a 

 fissure in the Carboniferous limestone near Frome, in Somer- 

 setshire ; and a molar tooth of Hypsiprymnopsis was found by 

 Professor Boyd Dawkins in Rhaetic marls below the " bone- 

 bed " at Watchet, also in Somersetshire. In North America, 

 lastly, there has been found in strata of Triassic age one of 

 the branches of the lower jaw of a small Mammal, which has 

 been described under the name of Dromatherinm sylvestre 

 (fig. 156). The fossil exhibits ten small molars placed side 

 by side, one canine, and three incisors, separated by small 

 intervals, and it indicates a small insectivorous animal, pro- 

 bably most nearly related to the existing MyrmecobL'.s. 



LITERATURE. 



The following list comprises a few of the more important sources of 

 information as to the Triassic strata and their fossil contents : 



(1) ' Geology of Oxford and the Valley of the Thames.' Phillips. 



(2) 'Memoirs of the Geological Survey of Great Britain and Ireland.' 



(3) ' Report on the Geology of Londonderry,' &c. Portlock. 



