152 DIVER 
attracted the attention of Willughby more than two hundred years 
since. On the other hand, Brandt, and Rudolph Wagner shortly 
after (Naumann’s Végel Deutschlands, ix. p. 683, xii. p. 395), had 
already shewn that the structure of the knee-joint in the Grebes 
and Divers differs in that the former have a distinct and singularly- 
formed patella (which is undeveloped in the latter) in addition to 
the prolonged, pyramidally-formed, procnemial process—which last 
may, from its exaggeration, be regarded as a character almost 
peculiar to these two groups.! The evidence furnished by oology 
‘and the newly-hatched young would seem to favour Brandt’s views; 
and, without according too much weight to such evidence, it cer- 
tainly ought to be considered before a decision is reached. The 
abortion of the rectrices in the Grebes, while these feathers are 
fairly developed in the Divers, is another point that helps to 
separate the two Families; but until their morphology has been 
worked out nothing can be safely averred on the subject. 
The commonest species of Colymbus is C. septentrionalis, known 
as the Red-throated Diver from an elongated patch of dark bay 
colour which distinguishes the throat of the adult in summer-dress. 
Notwithstanding this ornament, it is the least conspicuous, as it is 
also the smallest, species of the genus, the back and upper plumage 
being of a blackish-brown with a few insignificant white spots, 
while the head and sides of the neck are ash-coloured, bounded by 
a long nuchal band, which lower down advances towards the 
breast, of feathers marked with black, grey, and white, to form 
regular stripes. Immature birds want the bay patch, and have 
the back so much more spotted that they are commonly known as 
“Speckled Divers.” Next in size is the Black-throated Diver, 
C. arcticus, having a light grey head and a gular patch of purplish- 
black, above which is a semi-collar of white striped vertically with 
black, while two patches on the black back, between the shoulders, 
as well as the scapulars, are conspicuously marked with large sub- 
quadrangular white spots. Still bigger is the Great Northern 
Diver, C. glacialjs or torquatus, with a glossy black head and neck, 
two semi-collars of white and black vertical stripes, and nearly the 
whole of the black back and upper surface of the wings beautifully 
marked with white spots, varying in size and arranged in belts.” 
Closely resembling this bird, so as to be most easily distinguished 
from it by its ivory-white or yellow bill, is C. adamsi, the specific 
1 Garrod, in his tentative and chiefly myological arrangement of Birds 
(Proc. Zool. Soc. 1874, p. 117), placed the Colymbidw and Podicipedide in 
one Order (Anseriformes) and the Alcidx in another (Charadriiformes) ; but the 
artificial nature of this assignment may be realized by the fact of his considering 
the other Families of the former Order to be Anatid# and Spheniscidex. 
2 The osteology and myology of this species are described by Dr. Coues 
(Mem. Boston Soc. Nat. History, i. pp. 181-172, pl. 5). 
