NATURAL SCIENCES OF PHILADELPHIA. 181 



It is immaterial what name is given to the several assemblages of individu- 

 als that make up the genus. Some authorities admit but one, or at most two, 

 "species"; others six or eight. With a common standard of reference, both 

 parties cannot be right. If there be sucli a standard in nature, not dependent 

 upon the minds of ornithologists, the difference clearly results from the 

 fluctuating position that the latter have assigned to it; and a human fallacy, 

 one way or the other, is implied. If, on the contrary, no such standard exists, 

 one of the above mentioned views is as true as the other. As will be seen in 

 the sequel, the probability is that the latter proposition comes nearest the 

 truth. At any rate, during tliis discussion, until some conclusions are reached, 

 the terms "variety," "race," and " species" will be used interchangeably, as 

 may be most convenient for the designation of such groups as it may be 

 necessary to speak of, — not in the conventional sense that these words have 

 gained. And by the term ^'^■Ec/iothus " I wish to be understood as referring, 

 not to the abstract idea of the genus so designated, but collectively to the 

 million or more individual birds that are to day living upon the earth, as the 

 concrete expression of the genus they constitute. 



It is demonstrable, I believe, that these birds constitute a genus ; that is; 

 that they are separable from all other birds whatsoever, by a set of characters 

 of higher grade than those by which they have up to this time been differenti- 

 ated among themselves. There is no break or flaw in the bird by which it is 

 possible to circumscribe them. There is no shading into or graduating towards 

 this or that allied generic group. No bird has yet been discovered of which it 

 cannot be predicated, without qualification, that it either is, or is not, one of 

 the ^^giothi. If it is, it will be found to exhibit the following combination of 

 characters : and no bird, not presenting just this combination, is an jEgiothus : 



The culnien barely or not curved, as long as the middle toe without its claw, 

 and not over four-tenths of an inch long ; the upper mandible beset at base 

 with retrorse plumules, more or less concealing the nostrils ; the lower man- 

 dible without ridges ; the point of the wing formed by four primaries, of 

 nearly or absolutely equal lengths ; the length of the wing from carpus to tip 

 barely exceeding one-half the total length from tip of bill to end of tail ; the 

 tail four-fifths to five-sixths of the length, forked, with broad, rounded feath- 

 ers ; the middle toe without its claw uot over two-thirds as long as the tarsus ; 

 the hind claw longer than its digit ; the crown of the head some sliade of 

 crimson ; the colors of th» back not in well-defined areas ; the rump lighter 

 colored than the rest of the upper parts; the adult male with the breast of 

 some shade of red, and the throat unstreaked. 



It is common to speak of the " type of a genus," and in this instance A. li- 

 nariu.% is generally held to be such But it is evident that if the above charac- 

 ters of the genus were to be drawn exclusively from this species, they would 

 be rather specific than generic, and would require qualification. A diagnosis 

 drawn as closely from linarius alone as the foregoing is drawn from the six or 

 eight forms together, would exclude at least two, — rosfratus and canescens. In 

 fact, if such expression be allowable, it may be said that linarius rather ex- 

 aggerates than typifies ^■Egiolhm ; that is, makes ^32giothus out to be more dif- 

 ferent from other birds than it really is ; for rostratus, for instance, in the 

 features of size and shape of bill, more nearly resemble Linota or Leucosticte 

 than linarius does. It is only by weighing all the phases of the genus together, 

 taking an average, and weighing this against other averages, that a diagnosis 

 of the genus can be obtained. Upon this muthod I have framed the foregoing 

 definition, which I believe applies to JEgiothus alone ; and, as has been pre- 

 mised, it is highly satisfactory to find that the subject in hand may be so 

 definitely limited. I see no " type" of this genus, except in an ideal — certainly 

 no known existing— bird, that combines the attributes of all, without present- 

 ing exclusively the special characters of any, of the species. 



If there was ever a time when all the then existing ^■Egiothi resembled each 

 other as closely as those now called " linarius " do, — in other words, if the ge- 



1869.] 



