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Show 1886.] MR. R. COLLETT ON BAL^NOPTERA BOREALIS. 249 the narrowest point (just where the flukes commence) was in the largest specimen 390 mm., or about 15 inches. V. Colour. The colour of the back is bluish black or occasionally somewhat brown, much resembling the colour in B. sibbaldi, although the blue colour as a 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 terminates at the genitalia, but occasionally it is interrupted or imperceptible 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, sometimes only for a couple of feet. On the breast the white becomes narrower, and in many individuals 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 underside 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, sometimes, 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 X X V I . 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. ZOOL. Soc-1886, No. XVII. 17 |
