THE ANCIENT MAMMALS OF BRITAIN. $21 



Paris stands, and which are consequently assigned to the 

 lower part of the Oligocene ; the beds of Hordwell, in Hamp- 

 shire, and Headon, in the Isle of Wight, likewise belonging to 

 the same great division. The clays of Barton, in Hampshire, 

 which, like those next mentioned, unfortunately yield scarcely 

 any Mammalian remains, bring us to the upper portion of the 

 Eocene Period ; while the older clays of Bracklesham, in 

 Sussex, are assigned to the middle division of the same epoch. 

 Better known than these is the London clay, forming the 

 upper portion of the Lower Eocene, and yielding several types 

 of Mammals ; beneath which are the unfossiliferous Woolwich 

 and Reading beds, resting on the chalk. Before proceeding 

 to the consideration of the Fauna of these various beds, it may 

 be observed that Mammalian remains are for the most part 

 rare and fragmentary, and that for a full knowledge of the 

 extent of the Fauna of the period, and the structure of its com- 

 ponent items, we have to depend largely upon the discoveries 

 made on the Continent or in the United States, both of which 

 are more favoured than Britain in regard to the preservation 

 of early Tertiary Mammals. In our survey of the Fauna of all 

 these beds, it will be more convenient to treat of the animals 

 according to their zoological position, indicating the different 

 horizons in which they severally occur. 



At the present day Lemurs are chiefly characteristic of 

 Madagascar, although likewise occurring in Africa, and also 

 represented in south-eastern Asia, but in the Oligocene Period 

 they were abundant in Europe. One of these early Lemurs 

 was described from the Hordwell beds as far back as the year 

 1844 under the name of Microchcerus, but it is only recently 

 that its true affinities have been recognised. Not much larger 

 than a Squirrel, this creature approximated in the structure of 

 its skull to the African Lemurs known as Galagos, but differed 

 from all the existing members of the group in that the lower 

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