NATUKAL SCIENCES OF PHILADELPHIA. 129 



Tdrdcs nanus. 



Tardus nanus, Audubon, Orn. Biog. V, 1839, 201— Baird, Birds N. Am. 1858, 

 213. — Turdus [Hylocichla) nanus, Baird, Rev. Am. Birds, I, 1864, 15. 



Sp. ch. Above witli the clear darli olive of swainsonii, but this even purer 

 and more plumbeous. Upper tail coverts (but not lower part of rump) becom- 

 ing more rufous, the tail abruptly darker, richer and more purplish rufous, 

 approaching to chestnut. The clear olive of the neck passes into brownish 

 plumbeous along sides ; pectoral spots more sparse and less pure black than in 

 pallasi. The white beneath is of an almost snowy purity, appreciably dif- 

 ferent from the cottony white of pallasi. A very tangible and constant char- 

 acter possessed by this perfectly distinct species is the more slender and de- 

 pressed bill, as compared with that of 7>(?Wa««. Specimens vary only in inten- 

 sity of colors ; these variations very limited, and corresponding with those of 

 pallasi. In all cases, however, their precise pattern and peculiar distribution 

 is retained. 



TCRDUS AUDUBONII. 



Turdus (^Hijlocichld) audubonii, Baird, Rev. Am. Birds, I, 1864, 16. 



Sp. Ch. — Relative proportions of nanus, but much larger even than pallasi, 

 the bill much more elongate and slender. Plumage similar to that of pallasi 

 but lighter and more grayish ; the rufous posteriorly more restricted and more 

 yellowish even than in pallasi ; pectoral spots larger and more sparse than in 

 pallasi, clove brown instead of nearlj^ black, breast and neck almost entirely 

 destitute of any yellowish tinge. This species, the validity of which may by 

 some be questioned, diflers principally from pallasi in being much larger and 

 more slender, with the arrangement of colors as in nanus, although the shades 

 are more as in pallasi. 



In regard to the above mentioned thrushes, the discussion as to whether thev 

 be all descended from as many primitive creations, whether there be three 

 species with several varieties each, or finally whether all be merely modifica- 

 tions of one original type, would involve the opening of the whole question of 

 the origin of species, and what constitutes genera and species and need not be 

 prosecuted here. Whether one naturalist calls them species, and another 

 races or varieties, so much is, I consider, well established — that there are 

 seven forms of N. American thrushes requiring names, all of definable charac- 

 ters, and all having a well marked region of distribution. Also, that these 

 forms are permanent over a large area, but that as in many other instances 

 where the areas of two overlap, we have suddenly intermediate or hybrid 

 birds that are with difficulty to be referred to either; and that these interme- 

 diate birds mixing with the others in their migrations tend to obscure the 

 series ; but that, as a general rule, specimens taken in the breeding season are 

 distributed geographically and colored, as stated above. 



2. On the uniformly red species of Pijranga, with descriptions of a new JV. American 



species or variety. 



In treating of the species of this form of the genus Pyranga, I have en- 

 deavored to be as conservative as possible in my conclusions, and have, after 

 careful consideration of the species, represented in all their various conditions 

 by the immense series of specimens before me, made due allowance for the 

 variations which may accrue from natural causes, as difference of habitat, &c., 

 and in designating the species, have allowed to each the widest possible limit, 

 including all varieties as subordinate. 



Of the present group we find two styles, one with the Pyranga sestiva, Vieillot, 

 as type, characterized by large light colored bill, without conspicuous tooth on 

 commissure, and with no marked contrast between tints of upper and lower 

 surface. This group contains, besides the P. lestiua, the P. saira, Sclater, and 

 P. cooperi. The other, with the Pyranga hepatica, Swainson, as type, is distin- 

 guished by plumbeous-black bill with prominent commissural tooth, and tlie 



1869.] 9 



