THE COLOURS OF DESERT ANIMALS 143 



and East, and which agrees well with the colour of 

 the red sands upon which they were captured.'' 

 These authors also quote Prof. Spencer's field notes 

 made on the same expedition, with regard to an 

 Agamid Hzard {Amphibolurus barbatus) : " On open 

 country to south of Charlotte waters, a general 

 yellow-brown colour — similar to general colour of 

 ground, with withered grass, etc.," which is con- 

 trasted with the series collected "at Crown Point, 

 where plenty of red sand was, a peculiarly brick-red 

 colour much resembhng the colour of the sandy hills 

 close to the camp where it was found." It is 

 particularly interesting to find that this species so 

 closely resembles two different types of desert soil, 

 for it is widely distributed in AustraHa, and by no 

 means speciaUzed to a desert environment. The 

 birds, too, furnish the most beautiful examples of 

 species coloured so as to be well-nigh invisible 

 among their native stones so long as they remain 

 motionless. One of the Crested Larks {Galerida 

 theklce) is represented by a dark race (G. t harterti) 

 in the northern parts of Algeria, which are not 

 desert ; in the semi-deserts which fringe the Atlas 

 Mountains southwards this is replaced by a paler 

 race {G. t. hilgerti) ; in the Northern Sahara itself 

 a still paler race is found (G, t, deichleri), which " is 

 so wonderfully adapted to the soil that it is easily 

 overlooked if the birds do not happen to be on the 

 wing or singing " (Hartert). Between Laghwat and 

 Ghardaia a reddish form (G. t, carolince) of this 

 species is found, and its distribution corresponds 

 fairly closely with the reddish stony desert. The 



