328 GEOGRAPHICAL DISTRIBUTION 



whether it melts insensibly into that of the Nearctic area of the 

 Holarctic Region. It will be most convenient to consider that 

 Region next, though strong doubts may be entertained as to the 

 logical propriety of such a course, for this Holarctic Region seems 

 to have the most highly developed Fauna, in that it is one from 

 which the weakest types have generally been eliminated, though 

 that result is chiefly seen in its Palsearctic area, and perhaps espe- 

 cially in the western part of this, shewing the truth of the poet's 

 line happily applied by Mr. Sclater in his classical essay- — 



" Better fifty years of Europe than a cycle of Cathay." 



IV, The Holarctic Region. — As has been stated in the introduc- 

 tory portion of this article, the combination intimated by this 

 phrase, though sanctioned in spirit by Prof. Huxley, wholly con- 

 travenes the opinion expressed by two of the leading authorities 

 on the subject — Messrs. Sclater and Wallace. The arguments of 

 the former being based on positive facts, or at least on what seemed 

 at the time to be such, must be met by corresponding facts. Those 

 of the latter having a more hypothetical foundation — the notion 

 that each of the primary divisions of the earth's surface should 

 comprehend about the same extent — require less consideration. 

 The natural philosopher regards quality rather than quantity, and 

 things must be weighed as well as measured, analyzed as well as 

 surveyed. Scarcely any systematist nowadays doubts that among 

 Mammals the Monotremes, of which only two living Families are 

 known, form a Subclass at least as important as the Monodelphians, 

 the existing members of which may number nearly fourscore Families, 

 even if there be not an opinion that Monotremes are of equal rank 

 (in one sense of the word) with the Monodelphians and Didelphians 

 thereto added. But, not to wander from our present business, no 

 one who will investigate the Avifauna of that part of North America 

 lying outside the boundary (if it can ever be traced) of the 

 Neotropical Region, will find in the Nearctic area more than a 

 single Family of Birds that is peculiar to it, and that is a Family 

 of position so doubtful that some of those who have most closely 

 stiidied it refer it to one or another of well-known Families — 

 Paridm or Troglodytidss — both of which are widely dispersed and 

 admittedly contain genera that differ considerably. If by way of 

 accommodating these dissentient views we recognize Chamxa as the 

 type of a distinct Family — and in our present state of imperfect 

 knowledge no other course seems open — the existence of such a 

 Family, Chams&idx, still seems precarious. Every other Nearctic 

 Family is common to the Neotropical Region or to the Paltearctic 

 area, or to both. Of the Fasseres common to the Neotropical Region 

 and the Nearctic area 4 Families are admittedly better represented 

 in the latter — name] y, Mniotiltidx by some 13 genera and about 50 



