Vol. xiii.] 16 



the colouring of the crissum and under tail-coverts, which 

 in S. lugens is of a darker rufescent hue than it is in 

 S. halophila, in which latter species indeed it is sometimes 

 almost pure white. The size of the two species is also not 

 quite the same. 



" Canon Tristram, during his travels in Algeria, appears 

 to have met with adult males and females, as well as with 

 immature males, of the present species. The adult males he 

 referred to S. lugens, Licht., but the females and the imma- 

 ture males he took to belong to a new species, and called 

 them S. halophila (Ibis, 1859, pp. 59 & 300). This being 

 the case, his name, although given in ignorance of the real 

 state of matters, must stand. 



" Both Dr. Koenig (J. f. O. 1895, p. 376) and Baron 

 Erlanger (J. f. O. 1898, p. 231) have entered at some length 

 into the question of this interesting discovery, and the 

 former has given some good plates of the species, showing 

 plainly the difference between the adult male and female 

 as well as a very old female. 



" Seebohm, when describing the female of S. lugens 

 (Cat. B. B. M. v. p. 371) as quite different from the male 

 in plumage, must have had before him specimens which 

 were not from Egypt, but probably from N.W. Africa. 



" Loche (Expl. Scient. de l'Algerie, i. p. 207) appears to 

 have noticed the difference between the sexes of the present 

 species, but did not distinguish it from S. lugens. 



11 Mr. Dixon also appears to have noticed the difference 

 (Ibis, 1882, p. 562). 



" Mr. Dresser's plate of immature S. erythraa (Birds 

 of Europe, ii. p. 29) was taken from the type of Canon 

 Tristram's S. halophila. 



" The next of the four species is Sylvia deserti (Loche). 

 This appears to me to differ sufficiently from S. nana, H. & 

 E., to be treated as a good species. The difference between 

 the two, it is true, is merely one of colouring, the North- 

 west African bird being of an isabelline rufescent colour, 

 while S. nana from North-east Africa and Asia is dis- 

 tinctly grey in colour ; but the difference appears to be 



