182 PROFESSOR STRUTHERS. 



(17f inches in Megaptera, 17^ in B. musciilus) is obtained on a 

 shorter jaw in Megaptera (120f in Megaptera, 135 in B, mus- 

 cnhis), the curving is greater in Megaptera. This is apparent 

 to the eye. The greater width of the jaw in Megaptera and 

 the greater length in B. muscuhis are apt to mislead the eye in 

 regard to curvature. 



In regard to form, the body has a thicker appearance in 

 Megaf)tera on its posterior half, but this is deceptive, being due 

 to the less development of the upper border towards the coro- 

 noid process. The thickness of the body is not greater in 

 Megaptera than in B. musculus till near the symphysis. The 

 upper border in Megaptera is gently sigmoid, the convexity on 

 about the second quarter or more. The distal concavity is 

 mainly owing to rising up towards the symphysis, on the last 

 18 inches. 



[In B. musculus there is very little of the sigmoid character of the 

 upper border. This is mainly owing to the gradual rising of the 

 border to the high coronoid process, but there is a slight convexity at 

 about the second quarter of the border, and a slight rise towards the 

 symphysis, on about the last 20 inches. The most marked dis- 

 tinction of the body is its greater height on the first quarter in B. 

 musculus, rising gradually to the high coronoid process. This gives 

 the body its general tapering form, modified by the slightly sigmoid 

 upper border.] 



There is a difference on the lower border, taking the entire 

 mandible. Owing to the greater descent of the tuberosity, the 

 concavity at the lower border of the neck is much more marked 

 in Megaptera (2 inches deep) than in B. musculus (1 to Ij inch 

 deep). 



They differ at the symphysis, on the last 6 or 8 inches. In 

 Megaptera the lower border is more sloping; at 12 inches from 

 the end the height is 7 inches in both ; at 6 inches, it is the 

 same in B. musculus, half an inch less in Megaptera. 



Foramina. — Both series of foramina present differences. The 

 internal series in Megaptera, about fifteen in number, open 

 entirely in the groove. They begin 8 inches in front of the coro- 

 noid process, 1^ inch below the border, by two or three close 

 together, which rapidly form the groove. After an interval of 

 18 to 24 inches, a series of foramina open at intervals in the 

 groove, not requiring to ascend to it, except only that the more 



