114 PROFESSOR STRUTHERS. 



inferior, while in Megaptera the superior process is rather 

 broader than the inferior. 



Viewed from the side, the direction of both processes in 

 Megaptera is seen to be downwards, and the axis of the incom- 

 plete foramen is seen to have that direction in a marked degree. 

 In B. musculus the direction of the processes is nearly trans- 

 verse, and that of the axis of the ovoid ring outwards and a 

 little upwards. They differ also in the amount of the backward 

 slope. The surfaces of the upper and lower processes in B. 

 musculus are nearly on the same vertical plane, but in 

 Megaptera the lower process is on a plane anterior to the upper 

 process, partly at its junction with the body, and wholly so 

 externally, from its sloping much less backwards than the 

 upper process does. 



The adaptations of these differences appear to be that, in B. 

 musculus, the great breadth and flatness of the inferior process, 

 and the two processes being on the same plane, are related to 

 their having to support a great broad wing ; and that, in 

 Megaptera, the more backward slope of the upper process, as 

 compared with the lower, is in correspondence with the slope 

 of the same processes of the vertebrse behind it. The exception 

 is rather in the less size and rounded form, as well as the less 

 backward direction of the lower process in Megaptera. Its 

 circumference is 1 inch less than that of B. musculus ; the cir- 

 cumference of the upper process is 1 inch greater in Megaptera 

 than in B. musculus. In its rounded form and free termination 

 the lower process in Megaptera resembles the corresponding 

 part of that process in Mysticetus much more than in B. 

 musculus. 



S'pinoiis Process of the Axis. — The region of the spine of the 

 axis in Megaptera is very different from that of B. musculus. 

 In the latter there is the great square-shaped mass, formed by 

 the two thick lateral longitudinal ridges, and in the valley 

 between them the low median ridge, the true spinous process, 

 scarcely rising to the level of the lateral ridges. The lateral 

 ridges proceed backwards from the projections on which the 

 true anterior articular processes are situated. In Megaptera 

 the lateral ridges are low, proceeding backwards from the 

 anterior quasi-articular processes noted above with the atlas. 



