24 PROFESSOR STRUTHERS. 



50-feet-long B. musculus and in B. borealis, but in the latter 

 the anterior and posterior angles are bent rather inwards. 



In Megaptera the whole upper border is of great thickness, 

 except for about 9 inches just in front of the middle, where it 

 is of but moderate thickness. The thickness of the hinder half 

 (27 inches in length) increases backwards from If to nearly 

 2 inches. The anterior thick part (18 inches in length) in- 

 creases in thickness forwards from 1 to 1 J inches. The thinnest 

 part, above defined, is f inch thick. The posterior half has a 

 marked general curve, concavity inwards, the bay 1 inch deep. 

 The anterior half is gently sigmoid, the thinner part concave 

 inwards, the anterior and greater part convex inwards. Thus 

 the anterior angle is bent outwards as in B. musculus, while the 

 posterior angle is bent inwards. There are thus on the inner 

 side of the border two well-marked concavities, one on the 

 posterior half, the other just in front of the middle ; but on the 

 outer edge the convexity corresponding to the anterior con- 

 cavity is very little marked, owing to the thinning on the thin 

 part being on the inner side. The beams of the scapula, reach- 

 ing up to the thick parts on the border, are thus seen to be 

 broader than in B. musculus, the only thin part of the whole 

 scapula being that ascending from before the middle of the 

 glenoid cavity to the thin part of the border, showing itself as 

 a hollow in both directions on the outer surface of the bone. 



In Megaptera, the thickness of the bone increases on about 

 its upper third, so that the border, all along, is thicker than 

 the part of the bone near it. But in B. musculus, the thickness 

 continues to diminish upwards to the border, all along, except 

 where the border is very thick, close to its posterior and 

 anterior ends. 



Viewing now the surfaces of the scapula, the inner (venter) 

 presents none of those sharp ridges, radiating from the neck, which 

 are so well marked in B. musculus. In it they are seven or eight 

 in number, two running from the anterior border, the others 

 radiating from the neck, better marked on the anterior than on 

 the posterior half of the venter, and fully as well marked in the 

 50-feet-long specimen as in the more mature ones. These 

 ridges, with their intervening fossae, give the whole surface of 

 the venter a fan-like appearance. Viewed as a whole the 



