250 MR. R. COLLETT ON BAL^NOPTERA BOREALIS. [Feb, 2» 



long axis there runs a dark line, from which to both sides and both 

 ends run fine radii of similar lines '. 



These patches are most frequent on the sides of the body some- 

 what below the middle, and occur also on the tail, but may be found, 

 when they occur to any great extent, distributed singly right up the 

 centre of the back, and extending as far as the end of the lower jaw. 

 They occur on all examples, although they may not be equally 

 apparent in all. They evidently are due to a peculiar matter in 

 the skin, as they become more perceptible after the animal has 

 dried for a time. Single small white spots of a normal forui occur 

 less frequently in the black portion of the sides, especially up to- 

 wards the back. 



Among the markings of less constant occurrence m.ay be 

 noticed : — On one of the specimens examined there was a slightly 

 lighter patch behind the ear-opening, which began just at its pos- 

 terior margin, and extended backwards in a pyramidal form for 

 about a foot. 



In order to show the variations of the white colour on the belly, I 

 shall briefly explain its extent in the individuals examined by myself. 



No. 1. A female. — Throat entirely white; on the breast the white 

 area became narrower, though without being completely broken 

 off. A larger white patch occurred at the end of the furrows, 

 forming here an extension of the central stripe. On the belly the 

 white colour was partly covered over by the fine light bluish-grey 

 lines, which terminated as single white stains at the mammae. 



No. 2. A female. — The white area symmetrical and ample; 

 throat white, about ten furrows on each side being included, though 

 the upper ones were spotted with black. 



The patch became narrower backwards, so that between the 

 flippers only three furrows on each side were included, while behind 

 the flippers it spread out in an anchor-like form, the arms of which 

 extended rather high up on the sides (and to about half a flipper's 

 length from the end of the flipper). 



Behind the furrows the white area was almost interrupted by the 

 grey colour of the sides, but widened out again in front of the 

 mammae, where it was whitish and not sharply defined. The fine 

 bluish-grey lines were most frequent towards the dark portions of 

 the sides. 



In this specimen the oblong whitish marks on the sides were com- 

 paratively few and indistinct, although some of them were perfectly 

 white. 



No. 3. A female. — Throat white, the white commencing just 

 behind the symphysis of the jaw, and including the eight furrows on 

 each side of the central line; tliis white portion dnniiiished as it 

 passed backwards. Almost exactly under the distal end of the 

 flipper, when lying parallel to the body, it was broken off by the 

 colour of the sides, but it recommenced at the navel, and thence 

 extended unbroken to the mammae. 



• The general form and design reminds one of the septa in a Fungia or 

 HerpetolithxiB. 



