Xxil INTRODUCTION. 
That fine bird, the Great Northern Diver (p. 68), known 
only in England as a winter visitant, occasionally remains 
throughout the summer in Ireland and the Hebrides; and 
although the eggs have not been obtained yet in the 
British Islands, the bird is believed to have nested on a loch 
in Assynt, Sutherlandshire (cf. Harvie Brown, Zoologist, 
1868, pp. 1809, 1424). With reference to the occasional ap- 
pearance of the Puffin in winter, and the remarkable differ- 
ence which exists in the bills of individuals of different ages 
and at different seasons, the reader may be referred to the 
‘ Zoologist,’ 1862, p. 8003, and 1863, p. 8331. To the list of 
breeding-haunts of the Gannet given at p. 75, may be added 
one of the Skellig islands, off the coast of Kerry; and as the 
nesting-places of the Black-headed Gull (p. 77) are becoming 
not only fewer in number, but gradually smaller in extent, 
all records of their former or existing conditions must be of 
interest. The Gullery at Pillmg Moss, Lancashire, is de- 
scribed in the ‘ Naturalist,’ 1851, p. 194; that at Rollesby is 
noticed in the same periodical, 1854, p. 253. <A third colony 
on Walney Island is pictured in the ‘ Zoologist,’ 1864, 
p- 9156; while an account of the well-known Gullery at 
Scoulton Mere has been recently published by Mr. Stevenson 
(Trans. Norf. & Norw. Nat. Soc. 1872, pp. 22-30). 
With these fragmentary remarks it was intended to con- 
clude this Introduction ; but the reader may not unreasonably 
expect that something should be said in regard to the nomen- 
clature and arrangement of species which has been adopted 
in the following pages. On this head a few words will suffice. 
It must be evident to all who have paid any attention to the 
subject, that so long as naturalists continue to designate spe- 
cies at random by any synonyms which may belong to them, 
so long will confusion reign paramount, to the prejudice of 
all students in zoology. It is only by adhering strictly to 
