178 



Mr. Waterhouse stated, that in the construction of this table he 

 had endeavoured to display the geographical distribution of the sec- 

 tions of the order Rodentia, and that to accomplish this, it of course 

 became necessary to combine some system of classification, with an 

 arrangement of the genera according to the countries in which they 

 were found. The table is divided into five columns, one column 

 being devoted to each of the following portions of the globe: 1st, 

 Europe and North Asia; 2nd, North America; 3rd, Africa; 4th, 

 India and the Indian Islands ; 5th, South America and the West In- 

 dian Islands. 



In these columns the names of the genera found in each province 

 are inserted, and the number of known species belonging to each 

 genus (as nearly as can be ascertained) is also indicated. Horizon- 

 tal lines separate the genera according to the sections to which they 

 are supposed to belong. 



" The few Rodents found in Australia all belong to the family 

 MuridcB. About six species are known, and these appertain to the 

 genera Mus, Hapalotis, Licht. (which is the Conilurus of Mr. 

 Ogilby), Hydrotnys and Pseudomys. 



" The first thing that strikes the attention," observed Mr. Water- 

 house, " is, that the great mass of South American Rodents belong to 

 a different section from those of the northern portions of the globe, 

 and that they are of a lower grade of organization, as is also the case 

 with respect to the Old and New World Monkeys." 



The next point to which Mr. Waterhouse drew attention was the 

 relative number of species found in warm and in temperate climates. 

 " If the number of species found in the two provinces, Europe (in- 

 cluding North Asia) and North America, be added together, the 

 total is 180 species, whilst in all the rest of the world, taken together, 

 the amount is only 206 ; and if from this last number those species 

 which inhabit the temperate portions of South America and Austra- 

 lia (amounting to about 30) be deducted, and added to the first 

 amount, it would appear that the Rodents are most abundant in tem- 

 perate regions. In the Mammals of large size the case is reversed. 



" The total number of species inhabiting each of the provinces 

 pointed out in the table varies less than perhaps might be expected. 

 The European province, North America, and South America, arc 

 nearly equal as to the number of species they contain ; India and 

 Africa are also nearly equal, but they contain fewer species than 

 either of the other provinces. 



" The Squirrels, Rats, Porcupines, and Hares (constituting the 

 genera »S'cmn<5, 3Ius, Hystrix, and Lepus), are the only groups which 

 are found in all the provinces. 



" The Sciuridce abound most in North America and India, and 

 are least abundant in Africa and South America. In the latter 

 country they appear to be chiefly confined to the northern portions, 

 ^and are totally wanting in the southern. 



" The Muridce are about equally abundant in Europe, Africa, and 

 South America; in North America and India they are much less 

 numerous. 



