496 Mr. N. A. Vigors on the Natural Affinities 



The former groups, however, still retain their relation to the typi- 

 cal families of their own order, by frequenting for the most part 

 the inland lakes or rivers. The birds upon which we now enter 

 become more decidedly pelagic in their food and habits ; their 

 typical station in nature appears included within the limits of the 

 ocean, and their " business is in the great waters." We may have 

 remarked in the course of this inquiry, that the typical families of 

 an aberrant tribe or order are less perfect in their general con- 

 formation, than the families of the same group which deviate from 

 the type. This is necessarily the case. The tribe or order is itself 

 aberrant, and deviates from the more perfect structure of the con- 

 terminous tribes or orders that are typical in the more compre- 

 hensive division under which all are classed. The typical subdi- 

 visions of this aberrant tribe or order will consequently be those 

 which carry this deficiency to the extreme. In reference then to 

 their own division, the typical perfection of such aberrant groups 

 will consist, if I may so express myself, in their general imperfec- 

 tion — their strength will be in their weakness. To instance this 

 point we may refer to the order of Insessores, where the typi- 

 cal families of the two most aberrant tribes, the Tenuirostres and 

 the Fissirostres, exhibit less general perfection of structure than 

 the families which are less typical. In the former instance the 

 CinnyridcE and Trochilidce, the types of the tribe, evince in their 

 general organization a considerable degree of feebleness, both in 

 their bills and legs, in comparison with the strength displayed 

 in many groups of the aberrant Meliphagida and Nectariniadce. 

 We may observe the same character in the tribe of Fissirostres 

 also, where the general weakness of the structure of the typical 

 Hirundinidce and Caprimulgidce forms a striking contrast with 

 the comparative strength and robustness of many species of the 

 remoter groups Todidce, Meropidce, and Halcyonida. The pre- 

 valence of this principle in the groups that have already come 



before 



