INTRODUCTION. 
over the breast as vv^ell as the throat. The ear-coverts, and a crescent-shaped band separating 
the dark colour of the upper part of the neck from the green of the back, are yellow. In this 
section we find, for the first time, the upper tail-coverts destitute of any peculiar colour, and 
agreeing in tint with the adjoining part of the back. 
11 . Pter. macuUrostris with the bill white, marked on the sides of the upper mandible 
with about four large black blotches. 
12 . Pter. Culik\ with the bill red at the base, and black throughout the remaining two 
thirds of its length. 
G. The seventh and last section of the Ara 9 aris comprehends two species, distinguished by 
the simplicity of their colouring from all those which have been previously noticed. They are 
of a nearly uniform colour, and are entirely destitute of those striking tints which vary so 
agreeably the plumage of the remainder of the genus. In both of them the upper part of the 
throat is white; in one of them the cheeks also are white, while in the other they are blue. 
13. Pter. prasinus ; with the under tail-coverts and tips of the tail-feathers brown. 
14. Pter. sulcatus\ with the under tail-coverts of the same green as the belly, and the 
tips of the tail-feathers tinged with blue. 
In this last section, and especially in the last-named species, the bill acquires its maximum 
of deviation from the typical form of the family. Instead of being, as in the Toco Toucan, of 
greatly disproportionate length; compressed on the sides so as to be comparatively thin in its 
horizontal diameter while it is elevated in its vertical height; strongly arched along its upper 
edge, which is so narrow as to be almost sharp; and thin and light in its texture : it becomes 
in the Grooved-billed Ara 9 ari in every respect, as it were, condensed; its length is diminished 
so as to approach, in some degree, to the dimensions observable in certain Barbets, such 
as the Bucco grandis from the Himalayan mountains; its sides, though flattened and deeply 
grooved, are not approximated to each other, the horizontal or lateral diameter of the bill 
almost equalling its vertical height; the culmen is broad and flattened j and the whole sub¬ 
stance is comparatively solid, and conformable to the structure observable in the approxi¬ 
mating genera. In the form of its bill no less than in the colouring of its plumage the Pter. 
sulcatus is the most aberrant species of the family; it ought probably to be regarded as the 
type of a peculiar genus, and I should not have hesitated in so considering it, but for the 
intervention of the Pter. prasinus, which possesses most of its characteristics, though in a less 
marked degree, and which therefore connects it so immediately with the Ara 9 aris in general as to 
7 
