SYLVIADjE. 201 



In offering the foregoing characters as distinctions of the three primary divisions, 

 the ornithologist will bear in mind the difficulty of defining differences between 

 groups so closely united by imperceptible gradations in their aberrant forms. It 

 may, however, be observed, that the true Sylviadce are the most perfectly organized, 

 since they not only search for their food, like the Nightingales (Philomelince), 

 among boughs and trees, — catch insects upon the wing, like Flycatchers, but 

 are frequently seen on the ground, upon which they move with perfect facility *. 

 From the subtypical group the fly-catching habits seem to be withheld ; and, on 

 proceeding to the aberrant group, we find a still further diminution in the powers 

 of locomotion ; they are less varied, but more concentrated. The Saxicolince 

 walk, but do not explore trees, or habitually catch insects on the wing from a 

 fixed station. The Motacillince rarely perch, and never climb, yet they run with 

 amazing celerity. The Variance, again, are excluded from the ground, and from 

 capturing winged insects, yet they excel all others of their family in climbing 

 among branches. The genus Sylvicola, Sw., standing intermediate between the 

 true Titmice and the typical Sylvianw, present us, of course, with a union of both 

 habits. All these modes of progression are distinctly indicated by a corresponding 

 variation in the structure of the feet. 



We shall shortly notice the principal forms which enter into these groups. 

 The first, or typical circle, is marked by the following genera: — Sylvia, L. ; 

 Malurus, Vieil. ; Prinea, Horsf. ; Hyl'iota, Sw. ; and Cidicivora, Sw. The 

 second, or sub-typical, is indicated by Synallaxis ? Vieil. ; Curruca, Bech. ; 

 Philomela, Antiq. ; Phoenicura, Sw. ; and Thamnobia, Sw. ; but the affinities of 

 this latter group are by no means certain. In regard to the third, or aberrant 

 division, the ornithologist will immediately perceive the union of the Saxicolinw 

 with the Parianos, by looking to the following birds, having before him our well- 

 known Robin, as one of the first links in the chain : — Petroica multicolor, Sw. f 

 P. Lathami, Sw. % Setophaga (Erythrosoma) picta §, Sw. S. (E.) miniata, 

 Sw. ||, and Setophaga ruticilla, Sw. 



From the three primary divisions thus indicated, we proceed to the sub- 

 families, in which we have a perfect representation of the five principal groups 

 of the Merulidw, We shall, however, get a more accurate notion of the whole 

 family, by comparing it with the tribes of the Insessores. 



* This fact, in reference to the Sylvia hippolais, we have had frequent opportunities of observing in our own 

 garden, where the species is very common. — Sw. 



f Zoological Illustrations, second series, pi. 36. J Muscicapa Lathami, Vig., Lin. Trans., vol. xv., p. 205. 



6 Zool. 111., second series, pi. 2. || Synop. of Mexican Birds, No. 18. 



2 D 



