106 



NORTHERN ZOOLOGY. 



The great point, therefore, which is at issue, and upon which the natural arrange- 

 ment of the entire order of Insessores absolutely depends, is this : Are the Edo- 

 lianee or the Thamnophilinse one of the typical groups in the family of Laniadse ? 



It has been perfectly demonstrated by Mr. MacLeay (and we might give 

 numerous examples from the animal kingdom in corroboration of the fact), that the 

 two typical groups of every circle bear a close and intimate analogy, no less 

 than a direct affinity, to each other ; and that, when such groups are perfect, that 

 is, when the five leading forms in each have been detected, this relation of 

 analogy will be fully apparent between each. This, in truth, is perhaps the best, 

 as it certainly is one of the most severe tests, by which any supposed series of 

 natural relations can be tried. For although the naturalist, by the synthetic me- 

 thod, is perpetually in danger of confounding analogy with affinity ; of taking that 

 to be a form of transition, which subsequently proves to be one of representation ; 

 yet the strongest prejudice in favour of any preconceived notion can never so far 

 blind his judgment as to produce a double series of groups, having direct analo- 

 gies one to the other, and at the same time a positive affinity. Had the labours of 

 the profound observer who first detected this property of natural groups achieved 

 nothing more than this discovery, he would have deserved the lasting gratitude 

 of all succeeding naturalists. 



Now if the five types of form among the Lanianse and the Edolianse, or be- 

 tween the Lanianse and the Thamnophilinae, had been detected, the question might 

 at once be set at rest ; but, unfortunately, this is not the case ; and we must there- 

 fore inquire what characters of structure, or what peculiarities of habit, are shared 

 in common between a Lanius, a Thamnophilus, and an Edolius. The respective 

 peculiarities of each we shall now draw up in opposite columns, for the sake of 

 greater perspicuity. 



Lanius, Linn. 



Bill hard, universally short, 

 entirely compressed, the cul- 

 men arched from the base ; 

 the upper mandible furnished 

 with a distinct and prominent 

 tooth ; the lower mandible 

 thick and ascending. 



Thamnophilus, Vieil. 



EXTERNAL ORGANIZATION. 



BUI hard, more lengthened, 

 but entirely compressed, the 

 culmen curved only at the 

 end ; the upper mandible fur- 

 nished with a distinct and 

 sometimes prominent tooth, 

 but smaller than that of La- 

 nius ; lower mandible thick 

 and ascending. 



Edolius, Cuv. 



Bill not strong, generally 

 short, but sometimes length- 

 ened, compressed only on its 

 side, the base broad, culmen 

 arched from the base ; upper 

 mandible notched, but desti- 

 tute of any tooth ; lower man- 

 dible weak, straight, not as- 

 cending. 



