90 
Recent Literature. 
Understanding then the conformation of the bill, both in the breeding 
season and in the winter, it remains to show how the change is effected. 
The bird acquires its full breeding array in three ways : (1) by hypertro- 
phy, (2) by horny growths, (3) by coloration ; and, conversely, loses it in 
three ways, (1) by atrophy, (2) by loss of the horny growths, (3) by de- 
coloration. 
The transformations of the bill relate exclusively, as already said, to the 
hinder part. A. Upper Mandible : 1 . The horny boss is that forked 
piece which surrounds the base of the upper mandible. It is perforated 
with many little holes in regular oblique series, through which rudimen- 
tary 'perforating feathers pass out. In May, at the height of the breeding 
season, it is translucent, of a sort of flesh-color difficult to describe, more 
or less tinged with yellow or violet, rather variable in shade in different 
specimens. In falling off it loses this coloration, and becomes horn -yel- 
low, like any claw about to be shed. It generally comes off whole, but 
may break apart at the top, or towards the middle of either of its forks. 
Its fall leaves exposed the membranous boss, in which the perforating 
feathers are implanted, and which, the following season, reproduces a new 
horny boss. 2. The 7iasal buckler, situated in front of the horny boss, is 
forked like the last, and saddled on the upper mandible, having two broad 
triangular sides united. It falls off in three pieces, — one large and two 
small. The two little pieces (one on each side) called the subnasal lamel- 
la are always detached first ; the large saddle-shaped piece follows ; but it 
is so fragile that it is generally broken near the top before it finally falls 
off. The author, however, succeeded in securing one nasal buckler intact, 
this “ pre'cieuse piece corne'e ” coming from a wounded Puffin held by the 
wings, who clawed it off in trying to defend himself. The nasal buckler 
has the effect of causing a hard horny protuberance of the nasal region, 
and thus thickening the base of the bill. Its loss uncovers the nasal mem- 
brane, which in winter shrinks away from the forehead, and the following 
spring produces a new buckler. 3. The pre-nasal fissure establishes the 
separation between the nasal buckler and the first or great ridge ; in win- 
ter it is wanting, being replaced by the corresponding temporary groove. 
4. The transparent lamella is a horny pellicle of a beautiful orange-color, 
which covers the hinder part of the first or great ridge, and is so closely 
blended therewith as to be only distinguished in spring by its coloration. 
This lamella grows transparent when about to fall, and is detached by ex- 
foliation, exposing the first or great ridge, which is entirely red in winter. 
5. Ridges, and grooves. These are subject to no other changes than those 
resulting from simple desquamation and partial decoloration. B. Lower 
Mandible. Its transformations are still more curious and note- 
worthy. 1. The horny selvage is of the brightest orange in the breeding 
season. Its fall exposes the membranous selvage, which, yellow at first, 
soon loses its coloration. 2. The mental buckler represents both the nasal 
buckler and the transparent lamella. It comes off whole, its two sides joined 
