280 STUDIES, SCIENTIFIC AND SOCIAL chap. 



also America and Australia, and there are many similar 

 cases among insects. 



After what has been now advanced, the distribution of 

 the lemurs (which forms Dr. Sclater's fifth case) will offer 

 little difficulty. Every indication points to this being a 

 group of great antiquity, and to its having been once very 

 widely spread. Its still existing remnants are scattered 

 from Sierra Leone to Celebes, and from Natal to Eastern 

 Bengal and South China ; and they are so varied that they 

 require to be classed in three distinct families and thirteen 

 genera. Still more important is the proof of their extreme 

 antiquity afforded by the recent discovery, in the Eocene 

 deposits of the South of France, of a skull of an unmis- 

 takable lemur, allied to one of the still living forms of 

 West Africa known as the " Potto " ; while several other 

 fossils of the same age are also believed to belong to the 

 lemurine group. In North America, too, abundant remains 

 have been found in the Lower Eocene deposits, which are 

 believed to be intermediate between lemurs and the South 

 American marmosets. This clear evidence both as to the 

 antiquity and the wide range of the lemurs renders it 

 quite unnecessary to postulate any special changes of sea 

 and land to account for their actual distribution. In- 

 habiting Europe in Eocene times, they were probably 

 spread over the whole northern continent, and would as 

 easily migrate southward into their present habitats as 

 the hedgehogs, the civets, the chevrotains, or the porcu- 

 pines, which have all a somewhat similar, but far more 

 extensive distribution. Like the Centetidse, the lemurs 

 find Madagascar best suited to them, more no doubt from 

 the absence of competitive forms than from any peculiar 

 physical conditions. On the great continents they are 

 usually scarce, and are protected by their nocturnal habits 

 and by frequenting dense forests. They thus continue to 

 survive in the midst of creatures of a higher type and 

 more recent origin than themselves, and, together with 

 the opossums of America and some of the smaller mar- 

 supials of Australia, seem to have handed down to us 

 a sample of the forms of life which fiourished in the 

 earliest tertiary or even in mesozoic times. 



