318 On a Hybrid Thrush found in Norway. 



The generative organs of the hybrid were quite rudimentary, 

 and the sex could not be determined with absolute certainty. 

 I may remark that on various occasions I have dissected 

 about forty specimens of hybrid Grouse, and in none of 

 these have I found the sexual organs so indistinct as in this 

 bird. 



In almost all details the plumage of the hybrid was some- 

 what between the plumages of its supposed parents, and it is 

 not easy to determine which of them it most resembles. 

 Possibly the upper parts are most like those of T. pilaris, and 

 the lower parts those of T. iliacus. There is a broad buffy- 

 white line over the eye, nearly like that of T. iliacus. The 

 back is brown, but not quite of such a chestnut-brown as 

 that of T. pilaris. The head and neck are inconsiderably 

 lighter, and the rump olive-grey, a trifle darker than in 

 T. pilaris, but perceptibly lighter than the back. The chin 

 is almost unspotted, whitish with a huffish tint; the spots on 

 the breast are black and arrow-headed, not very like those 

 of either parent. The sides are reddish grey, the spots 

 somewhat ill-defined at their edges (not so much as in 

 T. iliacus) ; their colour is reddish grey in the middle, with 

 rather lighter edges, but with an indication of assuming the 

 triangular form, as in T. pilaris. The under tail-coverts are 

 whitish in their outer portions and reddish grey at their 

 roots. The tail is blackish, with broad greyish-brown 

 margins. The upper surface of the wings is most like that 

 of 7'. pilaris, but the second primary is of the same length 

 as the fifth. The under wing-coverts are reddish, but not 

 so dark or uniformly coloured as in T. iliacus. The longest 

 are lighter towards the tip, and the innermost are reddish 

 grey at the tips, but whitish at the base ; the feet are oE a 

 dark yellowish grey. The bill is blackish, the lower mandible 

 hoi'n-colour at the base. 



The diagnosis of this hybrid will therefore be as follows : — 

 Size halfway between those of T. pilaris and T. iliacus. Eye- 

 stripe broad, of a buflFy white. Upper parts most like those 

 of T. pilaris. Rump greyish brown, somewhat lighter than 

 the back. Lower parts most like those of T. iliacus ; the 



