1886.] MR. R. COLLKTT ON BAL.ENOPTKRA BOREALIS. 253 



of tlie dorsal fin. Tlie genital opening lies almost immediately in 

 front of tl>e anterior edge. 



The Inferior Maxilla. — The 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 4|, viz : — 



No. 2. .4-5. 

 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. rosirata, 5*5. 



Their greatest breadth (measured between the eyes) is, compared to 

 their length, as 1 to 1"7. This was somewhat less in a skeleton in the 

 Bergen Museum (total length SOj^ <^eel), 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 wiialebone 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 pL.tes; 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 riglit side 52 white plates, on 

 the left only 5 ". 



The number of the plates was about 3o0 in each jaw, in some 



^ Namely in the following manner : — On tbe right side the foremost 27 were 

 white in their outer half, and the next 15 quite white, after which caine 3 grey 

 plates. Then came 10 completely black, and finally 3 which were white with 

 black edges. Total 58. The remainder were black. 



Ou 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 36 plates were mottled with white, after 

 which came 16 quite white, the remainder being black. 



