♦ H 



COLLI' RIO. 



;i49 



j^rnduated. These differencos arc, however, most, appreciable in 

 gpt'ciirwjuH from th« middle and wostern provinces TIiohc from Uio 

 Western States, east of the Missouri River, as far north as Wiscon- 

 gin, are more intermediate between the two, althougli Htill near«!st to 

 the Rocky Mountain bird as described; the back darker, the rump 

 and axillars more plumbeous, the sides more bluinli 1 have little 

 doubt that the examination of scries from the States alonf? th« 

 Mississippi will show a still clo' ^r resemblance to typical C ludo- 

 vicianns, and that the gradation between the two extremes will bo 

 found to be continuous and unbroken. It therefore becomes a 

 question whether there is really more than one species, varying with 

 longitude and region, according to the usual law, the more western 

 the lighter, with longer tail ; or whether two species, originally dis- 

 tinct, have hybridized along the line of junction of their respective 

 provinces, as is certainly sometimes the case. The approximation 

 in many respects of coloration of the Shrikes of the Pacific coast to 

 those of the South Atlantic States, is not without its importance in 

 the discussion of the subject. Pending the decision of this question, 

 however, I propose to retain the name of excuhitoroides, as repre- 

 senting, whether as species or variety, a peculiar regional form, 

 which must be kept distinctly in mind. The comparatively greater 

 eize of the bill in the Cape St. Lucas specimens is seen in other 

 species from this locality. 



The intensity of the black front in this species varies considerably, 

 sometimes very distinct, and again entirely wanting. This may 

 probably be a character of the breeding season, the dulness of black 

 anterior to the eye, and the lighter color of the bill, having a close 

 relationship here, as in other species, to maturity, sex, and season. 



The essential differences between this species and the C excuhitor, 

 of Europe, will be found in the diagnosis given under the generic 

 head. They are qnite appreciable on a slight comparison. 



Siwcimens examined, over one hundred in number. The more 

 important localities are the following : — 



29 June. 1866. 



