GALERIDA CRISTATA MACRORHTNCHA 253 



as subspecies, and which, while differing from each other in certain 

 respects, still preserve the distinctive characters of the particular 

 group to which they belong. In their coloration and marking they 

 vary according to the particular district inhabited, thus, roughly 

 speaking, the birds frequenting the mountainous and more humid 

 region of the north are dark in colour, those found in the lower-lying 

 and drier central districts, paler, while those inhabiting the arid desert 

 country of the south are isabelline or sand-coloured. Owing, however, 

 to the fact of the modification in colour being, except where some 

 natural barrier, such as a range of mountains or a " Chott," exists, 

 more or less gradual and not defined by any hard and fast lines, the 

 subdivision of the species into forms or subspecies is extremely diffi- 

 cult, and it is impossible, in some cases, to say where one form ends 

 and another begins, or to draw any precise line of demarcation as 

 regards the habitat of eacli form. That these forms exist, however, 

 is undoubted, and it would certainly not be right, or to the advance- 

 ment of science, to ignore them. Wishing, therefore, to distinguish 

 the various forms found in Tunisia as appears most advisable and 

 convenient, I would propose the following subdivision, viz. : — 

 Galerida cristata (L.) group. 



(a) Galerida cristata macrorhyncha (Tristr.). 



(h) Galerida cristata arenicola (Tristr.). 

 Galerida theklse (Brehra) group. 



(a) Galerida theklce major (Brehm). 



{b) Galerida theklce superflua (Hart.). 



(c) Galerida theklce deichleri, Erl. 



id) Galerida tJieklm carolince, Erl. 

 Another form might perhaps be added to each group, but as I am not 

 quite convinced of the claim of either to distinction, I prefer, for the 

 present at any rate, not to separate them. 



The reason of the greater variation in the small-billed group as 

 compared with the large-billed group is no doubt due to the fact of 

 the former having a wider and more extended range in the liegency 

 than the latter. The small-billed Crested Larks are to be found 

 almost universally throughout the country, and frequent the hills and 

 high plateaux, as well as the lower ground, whereas the large-billed 

 birds are confined to certain districts and are, as a rule, only to be met 

 with on the plains. 



