382 PYCNONOTID.i\ 



with blaclf ear-coverts to the pale eastern forms with almost 

 white ear-coverts. At the same time, all along the joining line of 

 Molpastes li. hurmanicus, M. h. mgripileus and M. h. heiKjalensis 

 on the West with M. li. chi-ysoi-rhoides on the East we have not 

 only many intermediate birds, which miglit equally well be 

 assigned to either form, but there are many birds, tlie majority in 

 fact, which can quite definitely be credited to one or the other. 

 Thus there are in the British Museum Collection specimens from 

 the Shan States, Yunnan, Siara, Karenni, Tenasserim, etc., 

 some of which are labelled chrysorrhoides, some nigripileus, some 

 atricapillus and some Mossi but of the birds so labelled tliere are 

 many of which it is impossible to say to which race they belong. 

 Davison, Armstrong and others obtained birds at the same place 

 about the same date whicli they had no difficulty in calUng 

 chrysorrhoides or nigripiJeus, yet others again are referable to 

 either. It appears to me that all along the Siam-Burmese 

 boundaries there is a narrow region in which there is no stable 

 form found and where, evidently, there are such conflicting 

 conditions in the environment that Nature has not yet had time 

 to evolve one definite form. It is, of course, true that in all lines 

 of demarcation between geographical races intermediate forms 

 ore tlie rule but in this intervening territory intermediate 

 individuals are less common than such as can be definitely assigned 

 to one or the other of the races in the adjoining area. 



In view of the many individuals which are exactly half-way 

 between chrysorrhoides and their next-door neighbours, I propose 

 in this work to treat all the forms as geographical races of 

 hcpuiorrhous . 



Molpastes chrysorrhoides Tclossi Robinson, Bull. B. O. C, xli, 

 p. 12 (1921) does not seem to be maintainable; the Museum 

 series varies in wing measurements between 87 and 104 mm., 

 whilst the very large series of Chinese birds range from 90 to 

 107 mm., one huge bird from Amoy having a wing of 111 mm. 

 On the other hand, it is quite possible that the birds of West 

 Siam may be separable as somewhat smaller and darker on an 

 average. The series in the British Museum from that country is 

 insufficient to determine this point. 



Key to Sjyecies and Sidjspecies. 



A. Under tail-coverts red. 



((. The black of crown sharply de- 

 fined and not extending to the 

 hind-neck. 

 a'. Ear-coverts black and not dis- 

 tinguishable from the crown. 

 a". Back dark brown, feathers fp- 383. 



narrowly edged with white. M. hcemorrhous hcemorrhous, 

 h" . Back paler brown, feathers 



broadly edged with white . M. h. pallidus, p. 385. 

 v. Ear-coverts brown, contrasting 

 with black of crown. 



