86 



4 



closely resembles the female and young of the present species; indeed, judging from an examina- 

 tion of the skins alone, I should be very doubtful of the advisability of separating it as a distinct 

 species; but Dr. SevertzofF, who has had such ample means of comparing these Asiatic Thrushes, 

 and of observing them in a state of nature, assures me that it must be treated as distinct. This 

 species, which he has called Turdus mystacinus, differs but slightly from the female of Turdus 

 atrigularis in general appearance, in having the chin and centre of the throat white, the markings 

 being less generally diffused; the throat is washed with pale warm buff; and the markings on 

 the underparts are more drop-shaped than in the female of T. atrigularis. Dr. SevertzofF informs 

 me that the male never assumes the black throat as in T. atrigularis. His theory is that Turdus 

 mystacinus is the original species from which almost all the other species of Siberian Thrushes 

 have sprung, and that it will in time disappear, leaving the other forms which have gradually 

 diverged from it in different directions, as perfectly good and distinct species without any inter- 

 mediate specimens as connecting links. He brought with him a considerable series of specimens 

 showing the great individual variation in this species as illustrating his theory; and some of the 

 most interesting of these I still have. Amongst them I may mention one showing a great ten- 

 dency towards Turdus musicus, both in the coloration of the upper parts, and in the spotting 

 and marking of the underparts. I have not been able to compare it with Turdus auritus, Verr., 

 the Mongolian form of our Song-Thrush ; but it is not improbable that it resembles this species 

 perhaps more closely than it does Tardus musicus. I have also examples of both Turdus dubius 

 and Turdus naumanni in immature plumage which show a marked resemblance to some of the 

 specimens of Turdus mystacinus belonging to Dr. SevertzofF; and this gentleman assures me that 

 he has seen examples intermediate between this species or Turdus atrigularis and Turdus 

 ruficollis. Altogether the individual variation in these Siberian Thrushes is so considerable 

 as to make it by no means astonishing that so great confusion has hitherto existed in the 

 determination of the various species, and more especially in their synonymy. Although, as 

 will be seen by the lists at the foot of my articles, I have had a tolerably fair series for 

 examination, I find that it is by no means sufficient to enable me to work out as fully as I 

 should wish to do this question mooted by Dr. SevertzofF, and must reserve my opinion until 1 

 can gather together a much larger series of the various species than it is now possible to obtain. 

 The specimens figured are the adult male and female above described, both of which are in 

 in\ own collection. 



In the preparation of the above article I have examined the following specimens : — 



E Mus. II. E. Dresser. 



a, d ad. Chodjent, Turkestan, December 13th, 18G8 (Severtzoff). b, s ■ Chimkent, Turkestan, February 20th, 

 L866 (Dode). c,6juv. Chimkent, November 8th, 1866 {Severtzoff) . d,6 juv. Chimkent (Dode) . e,<$ ad. 

 (i wader, Baluchistan, December 1871 {W. T. Blanford). f, ?. Himalayas {Marshall), g, 6 , h, 6 , i, $ . 

 Simla {Tytler). k, <S juv. Lahore, March 7th, 1868 {Marshall). I, 6 juv. Nynetal, India {Marshall). 



E Mus. N. Severtzoff. 



a, $ . Taschkend, September 25th, 1871 (S.). b, 6 . November 25th. c, 6 . December 4th, 1874, Taschkend 

 (S.). d, 2 . Delta of the Oxus, September 25th. 



