MAMMALIA. 



67 



Among Myomorpha, it is interesting to notice that the 

 lemmings (Myodes lemmus and Guniculus torquatus) occur in 

 the Pleistocene of England. There are also remains of a 

 large dormouse (Leithia melitensis) found with the pigmy 

 elephants in the caverns of Malta. 



Pig. 63.- 



Table-case 

 18. 



-Left upper (A) and right lower (B) teeth of Beaver (Gastor fiber), 

 from the Fens of Camhridgeshire.; nat. size. 



Among Hystricomorpha, a skull of the gigantic Castoroides 

 ohioticus from the Pleistocene of North America is shown ; 

 and there is a drawing of a complete skeleton of this animal, 

 natural size, on the adjacent wall. There are also remains 

 of various genera from South America, where the extinct 

 Pleistocene Megamys (not represented in the collection) must 

 have been as large as an ox. 



The Lagomorpha, or rabbits, picas, and hares, date back 

 to the Oligocene period. 



Order VII.— SIRENIA. 



The extinct representatives of the "sea-cows," so far as 

 known, are very little different from the surviving members 

 of the Order. Eecent discoveries in Egypt merely suggest 

 that during the Eocene period they were most closely con- 

 nected with the early Proboscidean ITngulata. Various fossils 

 show that in Tertiary times they had a wider geographical 

 distribution than at the present day. 



Steller's Sea-cow (Ehytina gigas), which formerly browsed 

 on the sea-weed on the shores of Bering Strait, lived until 

 1782, when it was exterminated by the Eussian sailors who 



F 2 



Pier-case 

 29 (30). 

 Case V. 



