83 [Vol. xlii. 



and ground on which the nest is placed are very charac- 

 teristic of L. arhorea ; add to this the fact that the eggs 

 are very distinctive and cannot possibly be confused with 

 those o£ the Sky-Ijark, and identification is made compara- 

 tively easy. 



I exhibit twenty-five clutches of L. arborea, and thirty- 

 four clutches of A. arvensis for comparison. There is not a 

 clutch in either series which the trained eye could confuse. 

 In the series of A. arvensis you will find practically every 

 known form and variety. 



The eggs of L. arhorea run into three distinct forms ; 

 those with very fine mottlings which sometimes form zones 

 or caps at the larger end I consider typical. 



Form No. 2 have distinctly larger mottlings, of a warmer 

 shade of reddish-brown, consequently the zones and caps are 

 more conspicuous, and the general appearance is more 

 strikingly handsome. 



Form No. 3 (comparatively rare) have fairly large well- 

 defined blotches, which also have a tendency to form zones 

 and caps at the large ends. 



In some cases there is great variation in the eggs of a 

 single clutch, probably transition stage. 



A few examples show well-defined underlying blotches of 

 ash-grey. Compared with those of A. arvensis they are 

 considerably smaller, the ground-colour is whiter and less 

 concealed by the markings ; the pigmentation is distinctly 

 more rufous, and the formation of the mottlings finer on 

 the average. 



Compared with eggs belonging to the other members 

 of the genus which do not breed in the British Isles, I find 

 them closely allied to those of the Crested Lark, G. cristata^ 

 and certain forms of the Short-toed Lark, C. Iracliydactylay 

 though usually smaller than the former, and larger than the 

 latter. 



Average measurements (Rey's) : — Alauda arvensis, 24" 1 x 

 16*8 mm. Lullula arhorea, 20'7 x 15'5 mm. 



Average iveic/hts (Rey's) : — 182 mg. (100 eggs). 156 mg. 

 (46 eggs). 



