Recent Literature. 
89 
To get an idea of these remarkable changes (which the author illustrates 
as already described) it is first necessary to understand the composition of 
the bill in the adult in spring and in winter. Fratercula arctica, adult, in 
spring has the bill high at the base, with the under outline regularly 
curved from base to tip. The bill is divided into two very distinct parts : 
one posterior, which is moulted ; the other anterior, and persistent. 
1. The hind part is made up of a set of nine sutured horny pieces which 
come apart and fall off after the breeding season. Those of the upper man- 
dible are : (1) the horny basal boss, 2) the nasal buckler, (3, 4) the two 
(one on each side) subnasal lamellae, (5, 6) the two (one on each side) 
transparent lamellae, which cover the hind part of the first ridge ; and of 
the under mandible, (7, 8) the two (one on each side) horny selvages 
(corresponding to the boss on the upper mandible), and (9) the mental 
buckler. 
2. The fore part, which is persistent, shows three ridges and three 
grooves, designated, from base to tip, as the first or great ridge, the sec- 
ond or middle ridge, the third or lesser ridge ; the first or great groove, 
the second or middle groove, the third or lesser groove ; the bill ending 
with a smooth space, forming a triangle with curvilinear base, and termed 
the point of the bill. 
At the angle of the mouth a thickened skin, folded and scalloped, forms 
a large orange-yellow rosette. The ornaments of the eyelids consist of a 
thick vermilion-red edge, and two dark gray horny appendages, the upper 
one triangular, the lower elongate. 
Let us now see what the appearance is in winter, or after the breeding- 
season. The aspect is entirely different. The bill is smaller, as if cut 
away at the forehead, especially the under mandible, the outline of which 
is broken instead of forming a regular curve. W e still find the two well- 
distinguished parts already indicated in the breeding adult ; the fore 
part is intact, but the hind part is strangely modified by loss of the nine 
horny pieces. It has lost its thickness and its firm texture ; it is covered 
with a thick skin, which presents on the upper mandible (1) the membra- 
nous boss ; (2) the nasal membrane ; and on the lower mandible (3) the 
membranous selvage , and (4) the mental matrix. The commissural rosette 
is reduced to a narrow pale yellow band. The eyelids are uncolored, and 
have lost the horny appendages. 
cher mit einer Larve versehen, le Plongeon ci masque, the masked Diver, — a 
very suitable name, though any German reader will perceive that its composi- 
tion is not veiy happy. It is therefore not impossible that the true vernacular 
name was the first ; though ornithologists, not understanding the allusion to 
the change of the “mask,” w r ould see in the hnzl-tauscher nothing but the Ger- 
man name of Diver, Taucher. If der Larventauscher, Changeur de masque, 
Unmasker, is the real name of Fratercula arctica, it might be w-ell restored, as 
none could possibly be more appropriate or expressive. 
