1886.] MR. R. COLLETT ON BALZNOPTERA 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. 
Baléen black ; the bristles fine, white, and curling. The number of 
plates about 330 ; their greatest length 650 millim., not including the 
bristles. Jaws long, being to the total length about as 1 to 43. 
Balenoptera musculus, Comp. 1828. Norwegian Finhval 
(‘ Finner 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 63 or 63. 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 millim., not including the bristles. Jaws of moderate length, 
being to the total length as 1 to 5. 
Balenoptera sibbaldi, Gray, 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 53. 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 43. 
EXPLANATION OF THE PLATES. 
Prats XXV. 
Fig. 1. Side view of Balenoptera borealis, male. 
2. Lower surface of ditto, 
Piatt XXVI, 
Fig. 1. Lower surface of Balenoptera borealis, female. 
2. One of the pile pues 2 the skin ; enlarged. 
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Proc. Zooxu. Soc.—1886, No. XVIII. 18 
