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 lamella?, (5, 6) the two (one on each side) 

 transparent lamella?, 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 persistenj, 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. We 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 

 homy 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 verselien, le Plongcon a masque, the masked Diver, — a 

 very suitable name, though any German reader will perceive that its composi- 

 tion is not very 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," would see in the finsl-tauscher nothing but the Ger- 

 man name of Diver, Taucher. If der Larventauscher, Changeur de masque, 

 Un masker, is the real name of Fratercula arctica, it might be well restored, as 

 none could possibly be more appropriate or expressive. 



