1886.] MR. R. COLLETT ON BAL^NOPTERA BOREALIS. 265 



as a rule a little in advance of the last third of the body. Vent 

 placed exactly under hindermost edge of the dorsal fin. Flippers 

 unusually small, measuring about ^ of the total length of the body. 

 Baleen black ; the bristles fine, white, and curling. The number of 

 plates about 330 ; their greatest length 650 miUim., not including the 

 bristles. Jaws long, being to the total length about as I to 4|. 



Balcenoptera niusculus, Comp. 1828. Norwegian Finhval 

 (" Fiuuer Whale "). — Length 60 to 65 feet, seldom exceeding 70 

 feet. Form of the body very elongate ; the greatest height is to the 

 total length as 1 to 6| or Gf. Colour greyish slate above, also the 

 left lower jaw ; the whole underside, the right lower jaw, the inner 

 side of the flippers, and the underside of the flukes white. Dorsal 

 fin rather low, with almost straight margins ; it is placed some- 

 what forward, or very slightly in front of the last fourth of the body. 

 Vent placed just beneath the anterior edge of the dorsal fin. 

 Flippers rather small, measuring about \ of the total length of the 

 body. Baleen with the bristles dark bluish black or slate-colour ; 

 on the right side, the first rows are white or whitish. The number 

 of the plates between 350 and 370 ; their greatest length about 

 950 miUim., not including the bristles. Jaws of moderate length, 

 being to the total length as 1 to 5. 



Balcenoptera sibbaldi,Gra.y, 1847. Norwegian Blaahval ("Blue 

 Whale"). — Length about 70 to 80 feet, seldom exceeding 85 feet. 

 Form of the body more robust than the last species, the greatest 

 height is to the total length as 1 to 5|. Colour dark bluish grey, 

 with small whitish spots on the breast ; the lower edge of the 

 flippers and their inner sides white. Dorsal fin particularly low 

 and small, with straight margins ; it is placed far back, close to the 

 commencement of the last quarter of the body. Vent placed in 

 front of the vertical line from the anterior edge of the dorsal fin. 

 Flippers large, measuring about } of the total length of the body. 

 Baleen with the bristles black. The number of the plates up to 400 

 (according to Dr. Guldberg) ; their greatest length (according to Dr. 

 Nansen) 930 millim., not including the bristles. Jaws long, being 

 to the total length as 1 to 4g. 



EXPLANATION OP THE PLATES. 



Plate XXV. 



Fig. 1. Side view of Balcenoptera borealis, male. 

 2. Lower surface of ditto. 



Plate XXVI. 

 Fig. 1. Lower surface of Baltenoptera borealis, female. 

 2. One of the whitish spots on the skin ; enlarged. 



Proc. Zool. Soc— 1886, No. XVIII. 18 



