1920.] of the Mar ocean ^'Middle- Atlas y 283 



Firstly : — In to-day's physical map of Europe there 

 is much that suggests the individuality distinguishing certain 

 islands and parts oi the Continent ; but in this compact- 

 looking strip of Mauretania, surrounded by sea and desert, 

 Avith a mountain-tract all along its Mediterranean seaboard, 

 there seems little indicative of subdiAision. On the 

 contrary, there must be something in Marocco in addition 

 to its present surface features, Avhich gives it a distinct 

 individuality apart from the remainder of " Little Africa." 

 For example : of Mauretania's 122 Resident (non-Marine) 

 species, nearly ))0 per cent, either do not range over the 

 whole territory, or are disposed in two or more subspecies 

 throughout it as follows : — 



*17 species in Tunisia and Algeria are not in Marocco. 

 7 species in Marocco are not in Tunisia and Algeria. 

 10 species have subspecies in Marocco that differ from 

 the corresponding subspecies in Tunis and Algeria 

 (sometimes more than one in either case). 

 1 species only (the Chaffinch) has a different racial 

 division, viz. Marocco and Algeria/Tunis. 



This may, in part, be explained by the following : — 



(a) The Algero-Tunisian boundary is only a political 

 one : it is not indicated })hysically like the Algero- 

 Maroccan, by the abrupt termination of the Great- 

 and Middle-Atlas ranges, in the Ouad M'louya valley 

 and its adjoining tracts of desert and steppe. 



[h) Marocco's separation from the Sahara is abruptly 

 defined by the Great-Atlas, wdiereas Algeria and 

 Tunis both "peter out"' into the Sahara in a suc- 

 cession of arid steppes and plateaux — a fact that 

 accounts for their large number of desert forms. 



[c] Algeria and Tunis lack Marocco's Atlantic seaboard 

 which largely influences the climate and the passage 

 o£ migratory birds. 



* This figure is likely to be reduced sumewliat whou the south .slopes 

 of the Great-Atlas are better known. 



