( .503 ) 



The isolation and separation has j)rodnc-eil other difFerences — viz. size of wings 

 and bills, and even the colonr is nowhere qaite the same in isolated areas, thouich 

 it closely corresponds to that of the snrronndings. I hoi>e to illnstrate tliis 

 more exjilicitly wlien I have been able to bring together in the Triiig Miisncni 

 series from various districts, with sam])les of the sand or soil they live on. In 

 which way this assimilation to the soil takes away from the valne of these sub- 

 species, is incomprehensible to me. The local forms (snbspecies) are of conr>p 

 tlie jirodncts of the country they inhabit, but we do not as a rule know the 

 causes wliicli have j)roduced them. In many cases it is api>arently nothing bnt 

 isolation, and the isolated development of certiiin characters; in others ajiparently 

 climate, amount of rainfall, food, etc. ; in others again the colonr of the surroundings, 

 and this is more especially the case in ground-birds, which are assimihitcd to 

 the soil, rocks, steppe, sand, etc., which they inhabit. How this assimilation 

 took place we do not, at present, fnlly understand, but we must carefully study 

 and fix these varieties Ijefore we attemjit to explain tliem. 



DESCRIPTIOX OF TWO NEW BIEDS DISCOVERED BY 

 MR. O. T. BARON IN NORTHERN PERU. 



By G. E. IIELLMAYE, 



IX \'olume 11. of the Xovit. Zool., pp. 1 — 22, the late Mr. Salviu wrote an account 

 on the first collections made by Mr. Baron in Northern Peru, but about the 

 fuitbor consignments no full account lias as yet been published. Among the birds 

 sent by JNIr. Baron to the Tring Museum there are two more new forms, which may 

 be described as follows : — 



Thripophag'a berlepschi n. sp. 



^. Forehead and crown, as well as rump and upper tail-cox-erts, pale olivaceous 

 brown, the latter slightly tinged with rufous ; nape and back bright cinnamon-rufous, 

 in strong contrast to the colour of the head and rump. Upper wing-coverts bright 

 cinnamon-rufous, the middle and greater series blackish on the inner webs. (Juills 

 blackish, einnanion-rufous on the outer webs, tertials on both webs; tail uniform 

 cinnamon-rufous, a trifle paler than the back. Lores dirty whitish, cheeks iind ear- 

 coverts jiale brown, faintly washed with einnamou ; round the eye, especially above, 

 there is a slight whitish admixture ; sides uf the neck and chest bright cinnamon- 

 rufous, throat and chin decidedly jialor and more cinnamon-brownish ; breast and 

 abdomen pale oli\aceous brown, the under tail-coverts pale fulvous brown ; axillaries 

 cinnamon-rufous, under wing-coverts ochraceous, quill lining rusty bufif. Basal lialf 

 of the ujijier mandible horn-coloured, apical half and the lower mandible whilish. 



Wing 77 ; tail 87 ; tarsus 23 ; l>ill 16J mm. 



Type: c? ad. Leimabamba, N. Peru, Id.OOOfl. clev., July 13tli, 1H9-4. (). T. 

 }5aron coll. " Eyes orange." 



This fine new species is qnitc unlike any (illier member of the genus in 



