140 PROFESSOR STRUTHERS. 



tion. The end of the wing of the sternum has been covered by 

 cartilage ; the surface, 2| inches by 1J, facing outwards, with a 

 little obliquity upwards and backwards. The rough mark for 

 the ligamentous attachment, seen best on the left side, is on 

 the oblique posterior border of the bone, formed by the hinder 

 edge of the wing and the side of the broad base of the posterior 

 process. It is 4J inches in length, f inch broad externally, 

 narrowing gradually to J inch at the inner end. It has not 

 been covered by cartilage. In contrast with the nearly rectan- 

 gular recess between the wing and the posterior process in B. 

 musculus, this part in Megaptera is thus filled up, giving an 

 oblique posterior border to the bone, and contributing to its 

 diamond form. The ligamentous mark does not extend back 

 upon the narrow part of the posterior process, on which a sharp 

 edge separates, for the last 2J inches, the flat upper surface 

 from the convex side of the process. But the ossification here 

 is not complete on the right side. On the right side of the 

 upper surface there is a sub-cartilaginous area, 3f inches in 

 length by f inch broad, extending to the very point. Further 

 ossification of this cartilage backwards might have elongated 

 the process, and further outward growth of its anterior part, and 

 of the neighbouring part of the wing, would have filled up the 

 border on the right side to the same extent as on the left. The 

 partial concavity or oblique recess behind the wing on the right 

 side corresponds to the presence of a greater projection on the 

 anterior angle of the rib on the right than on the left side. 



[In the B. musculus the rough mark for the terminal joint extends 

 for 2|- inches on the wing and for 3^ on the posterior process, to the 

 part where the process becomes considerably narrower, 2 inches from 

 the point. The part of the mark situated on the process is much 

 broader (1^ inch) as well as longer than the part on the wing. On 

 the left side the side of the process is quite flattened by the mark, 

 and the recess between the process and the wing is deeper than on 

 the right side. The asymmetry here may be related to the greater 

 breadth (by nearly 1 inch) of the left than the right rib, at the end. 

 On the hinder border of the wing there is an interval of 2| inches 

 between the mark for the internal joint and where the outer end of 

 the wing begins to be sub-cartilaginous. The interval, however, is 

 rough, as if it had attached a ligament. The first rib shows a dis- 

 tinct rough elevation on its anterior border, for the lateral costo-sternal 

 articulation, beginning 4 to 5 inches from the end of the rib and 



