1914-15.] The Baleen Whales of the South Atlantic. 15 
general form the outline of the beak was triangular ; the base was 8 5 cm. 
broad when measured in a straight line, but 11 cm. across^the median ridge 
on the dorsum ; the apex was vertically flattened. Over a dozen short, 
delicate Hairs formed a scanty beard at the tip of the lower jaw; a few 
scattered hairs were seen at the margins of the beak, also immediately 
below the lower lip and on each side of the anterior nares.^' 
The Dorsal Fin projected from the mid-line of the back vertically 
above the genital opening. It was only 2 cm. (f in.) high, and its base 
of attachment was 3'7 cm. Its shape was falciform, the colour grey on 
the surfaces, black on the convex anterior border. 
Fig. 3. — Profile of Head with Pectoral Fin of Foetus of Baloenoptera rostrata. Reduced. 
The Tail was horizontal. Its posterior border was divided by a mesial 
notch into two symmetrical lobes, each of which had a thickened anterior 
border and a sharp posterior border, and ended in a somewhat pointed tip : 
the breadth between the opposite tips was 15*5 cm. (6 in.). 
The Ventral aspect was for the most part either convex or flattened; 
but from the anus to the tail the sides were laterally compressed, and 
a mesial ridge was produced both ventrally and dorsally. The skin of 
the ventral surface of the mouth, throat, and as far back as the pectoral 
limbs presented numerous shallow furrows and ridges placed antero- 
posteriorly ; they were the rudimentary representatives of the remarkable 
tegumentary folds which form so striking a character in the Rorquals. 
* Arnold Japlia has figured (Spengel’s Zoolog. Jahrh., xxxii., 1911) hairs on the chin, 
lower jaw and upper jaw of foetus of B. rostrata. W. B. Benham had previously described 
about 30 hairs on the chin and jaws of a young B. rostrata {Trans. New Zealand Inst., 1901). 
