1886.] MR. R. COLLETT ON BALEZNOPTERA BOREALIS. 253 
of the dorsal fin. The genital opening lies almost immediately in 
front of the anterior edge. 
The Inferior Maxilla.—Yhe length of the lower jaw-bones (mea- 
sured to the angle of the mouth in the non-skeletonized animal) is, 
compared to the total length, as 1 to 43, viz :— ; 
INOsp2eekeae 
No. 3.. 4:5. 
No. 5..4°7, 
No. 6..4°4. 
In this last specimen the lower jaw-bones, probably on account of 
their weight, were displaced, which is often the case. ‘The jaws have 
the same relative length as B. sibbaldi, and are longer than in the 
other two species. In these three species the proportions (according 
to Sars) are as follows :— 
B. sibbaldi, 4-5. 
B. musculus, 5:0. 
B. rostrata, 5°5. 
) 
Their greatest breadth (measured between the eyes) is, compared to 
their length, as 1 to 1°7. ‘This was somewhat less ina skeleton in the 
Bergen Museum (total length 307; feet), where the breadth across 
the temporal bones (according to Lilljeborg) was, compared to the 
length of the skull, as 1 to 2°0. 
VII. Baleen. 
The colour of the baleen is usually black and the bristles white ; in 
some individuals, however, a small number of the foremost rows were 
white, or mottled with white, but not symmetrically in each ramus. 
Besides the baleen in the six specially examined specimens, I examined 
a considerable quantity of whalebone which lay heaped up on the 
beach at the different establishments. Amongst all this, I only 
found two specimens which differed from the others in having some 
white mottled plates; in all the others it was entirely black. Of 
these two individuals, one had on the right side 58, and on the left 
53 of the foremost baleen-plates mottled ', 
The second specimen had on the right side 52 white plates, on 
the left only 5°. 
The number of the plates was about 330 in each jaw, in some 
? Namely in the following manner :—On the right side the foremost 27 were 
white in their outer half, and the next 15 quite white, after which came 3 grey 
plates. Then came 10 completely black, and finally 3 which were white with 
black edges. Total 58. The remainder were black. 
On the left side the colouring was somewhat similar. The first 31 were 
semi-white, and the next 9 quite white, then followed 3 blackish grey, after 
which came 3 white, then 2 greyish black, and finally 5 white. Total 53. The 
rest were black. 
* In this specimen on the left side the 5 foremost ones were white, all the 
others black ; on the right side the first 86 plates were mottled with white, after 
which came 16 quite white, the remainder being black. 
