THE RIGHT WHALE OF THE NORTH ATLANTIC. 913 
of the lungs prior to diving, that they can remain below the surface of the sea for 5 to 
10 minutes, or even 20 minutes or longer when feeding, as was observed by ScoRESBY. 
The same authority also related that when struck by the harpoon they can descend to 
a depth of 400 fathoms, and under special circumstances to 700 to 800 fathoms. 
An idea may be formed of the capacity of the thorax in the state which corresponds 
with complete expiration by articulating to a dorsal vertebra the first pair of ribs 
which belong to it, and by adapting the sternum between their ventral ends (fig. 20). 
The 1st dorsi-costal segment was 3 feet 5 inches in its greatest transverse diameter, 
and 8 feet 33 inches in its dorsi-ventral diameter. These measurements gradually 
increased to the 6th segment, in which the ribs had the maximum length and curve, 
when the transverse diameter was 7 feet 4 inches and the dorsi-ventral 5 feet 6 inches 
(fig. 20,D6). Further back the length and curve gradually diminished, and in the 14th 
segment the ribs were so short and had so feeble a curve that they exercised practi- 
eally no influence on the dimensions of the thorax. In biscayensis as in mysticetus the 
thorax in its general form was barrel-shaped, due to the wide curve of the majority of 
the ribs, which contrasted with the form of the skeleton in the Fin Whales (Balzeno- 
pteridze), in which the side walls were more flattened. Hopp, who figured the entire 
skeleton of the New York Right Whale, saw 14 pairs of ribs in it and in the other 
skeletons described in his memoir. Another specific distinction between biscayensis 
and mysticetus is therefore to be recognised. The ribs of B. australis have been 
figured by vaN BENEDEN. 
PrEcTORAL LIne. 
Scapula.—A large plate-like bone which measured 4 feet 14 inch in length 
between the anterior and posterior angles, and 3 feet 4 inch in glenoido-vertebral 
Fie. 21.—Right scapula, dorsum. 
TRANS. ROY. SOC. EDIN., VOL. XLVIII., PART IV. (NO 33). . 135 
