THE RIGHT WHALE OF THE NORTH ATLANTIC. 914 
STERNUM. 
The Sternum or breast-bone consisted, as in the Baleen Whales generally, of a single 
plate-like segment,* with which the 1st pair of ribs had articulated. The base or 
anterior border was deeply notched and the outline was cordiform, the posterior border 
was prolonged into a blunted apex, each lateral border was thickened in its anterior 
half and formed an articular surface for the Ist rib. The ventral surface was a little 
convex, and the superior or thoracic surface was concave. The greatest breadth at the 
base was 21} inches, the length from the apex to the cordiform notch was 13 inches, and 
to the most projecting part of the anterior border 18} inches (fig. 19a). The cordiform 
Fic. 194.—Sternum B. biscayensis. Fic, 198.—Sternum B. mysticetus. 
sternum in biscayensis has been figured by Gasco and GuLpBerc, whose drawings 
have been reproduced by Truz. In mysticetus the sternum has been carefully 
described by Sir Joun Srrutuers.t In one specimen the base showed a shallow cordi- 
form concavity, in the other the base was pointed. The latter bone, presented by him 
to the University Anatomical Museum, was 27 inches long by 20 inches at its broadest 
part ; it had only one costal articulation on each side, and its posterior end was attenuated 
(fig. 198). 
The sternum of B. biscayensis has been figured by CaPELLINI, Gasco, GULDBERG and 
TrvE; that of B. mysticetus by Escuricur and Remnsarpvt, STRUTHERS and TRUE. 
* I figured many years ago the sternum of a fetal Balzxnoptera sibbaldi which had a small supplementary 
second segment (Journ. Anat. and Phys., vol. iv., 1870, and Marine Mammals, op. cit., 1912). 
+ Journ. Anat. and Phys., vol. xxix., 1895. Fig. 198 is from one of his specimens. 
