214 Mr. A. R. Wallace on the Natural Arrangement of Birds. 



of the Parrot tribe and to no other birds. Their bill is an ap- 

 proach to that of the Parrot ; the upper mandible being thick, 

 much curved, and acutely pointed, while the lower is much 

 smaller and nearly straight, — a form quite different from that of 

 the Finches. The feet are very peculiar, the hind toe being- 

 small and capable of being turned forward. The tongue is de- 

 scribed as cartilaginous and flat, — one step from the ordinary 

 horny-tipped tongue to the fleshy one of the Psittacida. We 

 consider therefore the Coliida to be more nearly allied to the 

 Parrots than any other birds, and to be an isolated link serving 

 to connect them with the other Scansores in the direction of the 

 Musophagidce. 



In the accompanying diagram we have endeavoured to lay 

 down the families of Scansorial birds, so as to represent their 

 respective affinities; but the very imperfect and fragmentary 

 state in which according to our views the group exists, prevents 

 our arriving at a very satisfactory result. 



We may here remark, that we can never hope to arrive at the 

 true direction and amount of the affinities of the several families 

 of birds, owing to our complete ignorance of the extinct forms. 

 It is probable that in very few cases is there a direct affinity be- 

 tween two groups, each being more or less distantly related to 

 some common extinct group, so that we should represent their 

 connexion more accurately by making our central line a blank, 

 for the extinct portion of the group, and placing our families 

 right and left, at diff"erent distances from it. We should thus 

 see the reason why we so rarely find one family or genus exactly 

 intermediate between two others. For instance, though the 

 Cuckoos are by their feet intermediate between the Turacos and 

 Toucans, yet their diff^erent plumage and their insect food show 

 that they are more properly a lateral branch from some common 

 central group now extinct. 



Having thus determined the extent of the two groups which 

 can be separated from the Passerine birds, there remains an ex- 

 tensive series of species which we believe constitute one great 

 group of equal value with those we have already defined. This 

 group may be called the normal or typical Passeres, and consists 

 of about thirty-five families, containing between three and four 

 thousand species, or at least half of the known birds. These we 

 believe are too intimately connected with each other to allow of 

 their being separated into a few great divisions without violating 

 many of their natural relations. They have all normal or ^-toed 

 feet, which are never so short or weak as to be unadapted for 

 progression. The bill is always moderate in size and form, and 

 in the few cases where it is peculiarly modified, as in some spe- 

 cies of Dendrocolaptes, other species in the same family possess the 



