1886.] MR. R. COLLETT ON BALHZNOPTERA BOREALIS. 249 
the narrowest point (just where the flukes commence) was in the 
Jargest specimen 390 mm., or about 15 inches. 
V. Colour. 
The colour of the back is bluish black or occasionally some- 
what brown, much resembling the colour in B. sibbaldi, although 
the blue colour asa rule is less pronounced than in that species. 
The colour after death is darker than in the living animal. On the 
side of the body the colour becomes somewhat lighter; the belly is 
dark steel-grey with a white area running along the centre; the 
white colour begins at the symphysis of the lower jaw, and termi- 
nates at the genitalia, but occasionally it is interrupted or imper- 
ceptible on the middle portion of the belly. 
Considerable variations occur in the breadth, size, and form of this 
white part of the belly. The throat is always white, occasionally 
throughout its entire breadth. scmetimes only for a couple of feet. 
On the breast the white becomes narrower, and in many indi- 
viduals is completely cut off by the bluish-grey colour of the sides, 
but it then reappears on the belly, and continues in a somewhat 
irregular width to the genitalia. Behind the vent the whole under- 
side of the tail is light bluish grey, about the same as the back. 
The white colour is not always symmetrical, but is occasionally 
broader on one side of the middle line than on the other; also the 
extent of it on the belly may be rather irregular. On the throat 
similarly the white colour is sometimes broader on one side than on 
the other. ; 
The white patch on the belly was never absent in any of the 
specimens examined; and this observation is confirmed by all the 
managers of the whaling companies, who state that it is always to 
be found, though it is sometimes only slightly developed. 
The white colour, especially on the throat, is pure and sharply 
defined. On the belly and in front of the genitalia there are, on 
the contrary, a large number of very fine bluish-grey lines, which 
are quite short and run parallel to each other; these lines, which 
can only be distinguished when you are near to the animal, some- 
times, when they are very numerous and closely set, detract from the 
whiteness of these portions. 
The flippers are coloured on the outer side like the back ; on the 
inner side they are a trifle lighter, especially along the lower edge: a 
few individuals (such as No. 2 of the specimens examined) have large 
whitish spots on the inner side ; these are never, however, absolutely 
white. The flukes of the tail are also bluish grey underneath ; the 
dorsal fin is exactly the colour of the back. 
Distributed over the dark parts of all the specimens examined 
were a greater or less number of whitish oblong spots of peculiar 
form and colour, their length being about 100 mm., and breadth 
about 30 (Plate XXVI. fig. 2). Their outer edges are not always 
sharply defined ; their colour is in general whitish grey, occasionally 
almost white, and more rarely dark grey. Along the centre of the 
Proc. Zoo. Soc.—1886, No. XVII. i7 
