THE WHALEBONE WHALES OF THE WESTERN NORTH ATLANTIC. 121 
it is all dark (blue-black), but on the right side, as Schlegel has stated, the foremost 
is of a light yellow-white color. 
“The bristle-like fibres, into which the whalebone resolves itself on the inner 
side, are uniform yellow-white on both sides [of the mouth ].” 
All these peculiarities of color were observed in specimens taken at Snook’s 
Arm, Newfoundland, in 1899, namely (pls. 8 to 11), the narrow inferior white 
caudal margin, the antero-inferiorly-directed, narrow, dark mark reaching forward 
to the anus, the areas of dark color below the root of the pectoral, the white mark 
anterior to the root of the pectoral, with its streaks directed forward and back- 
ward, the dark-streaked white anterior border of the pectoral, the white right 
lower and upper jaws, and whitish anterior right whalebone. In no two individu- 
als, however, were the amount and disposition of the dark color precisely the same, 
while the want of uniformity of color on the two sides of the body was always 
conspicuous. As in land animals, there were very pale individuals and very dark 
individuals, and others which represented neither extreme. In some the inferior 
caudal margin was entirely dark forward to the anus, and very large dark areas 
invaded the white of the belly, while the inferior surface and anterior white 
margin of the pectorals were streaked with dark color, and all light markings were 
restricted and obscured. In other specimens the white inferior caudal margin was 
broad and the post-anal dark marks indistinct; the dark color hardly passed below 
the level of the pectorals, leaving practically the whole belly white, and the white 
markings about the base of the pectorals were large and distinct. 
In the midst of these variations, however, the presence of a dark left lower 
lip (pl. 11, figs. 8 and 4), white right lower lip, and white anterior right whale- 
bone remained constant, and the right side of the body never carried so much 
dark color as the left. This peculiar asymmetry of color, or “pleuronectism,” 
was first pointed out by Sars in 1878. Guldberg has more recently asserted that 
it is not exclusively confined to one side, or, in other words, that an individual 
might be light on the left side and dark on the right side. My own observations 
on American specimens do not bear out this statement. The right side in these 
was always lighter than the left side, and I am disposed to think that this isa 
constant character of the species. (See pl. 9, fig. 3; pl. 10, figs. 1 and 3; pl. 12, 
figs. 1 and 2.) 
VARIATION IN COLOR OF BODY. 
The individual variation in the amount and disposition of the white and gray 
colors of the body has already been referred to. It may be of interest to enumerate 
the differences in some of the Newfoundland Finbacks, from notes made on fresh 
specimens. 
In ten specimens the variations were as follows: 
No. 2. Female. Length, 64 ft. 8 i. General color dark. Below the left 
pectoral 35 furrows in the direction of the median line are dark colored. The 
remaining median furrows are white, with a flesh-colored tinting. Left mandible 
and upper jaw dark gray. The former whitish internally. Beginning at the 
