112 PROFESSOR STRUTHERS. 



in the spine. In all the specimens of B. musculus, the spine, 

 besides being low, is much more developed on the posterior half 

 of the arch, in two of them very little developed on the anterior 

 half. In Megaptera it is higher (1| inch, against about I inch 

 in the B. musculus), is semicircular in form, and rather better 

 developed on the anterior than on the posterior half. In con- 

 nection with this more anterior development of the spine is to 

 be noted the straightness of the anterior border of the lamina 

 in Megaptera, and also its thickness (f to | inch), while in B. 

 musculus it is a depressed sharp border. 



Transverse Processes of the Atlas. — While the transverse 

 processes of the specimens of B. musculus differ from each other 

 in detail, those of Megaptera have characters distinct from them 

 all. The difference is mainly in their shortness (in Megaptera 

 3f inches, in the 50-feet-long B. musculus 61). The farther out 

 position of the internal intertransverse tubercle (external to the 

 line of the outer edge of the condyloid cup, and at about the 

 middle of the upper edge of the process) gives the process a 

 more square shape in Megaptera, as seen antero-posteriorly. 

 The process is also broader externally in Megaptera, but this is 

 mainly owing to its wanting the outer half, which forms the 

 tapering, bent-back, and twisted part of the process in B. mus- 

 culus. The breadth (height) of the process at the middle, at the 

 internal intertransverse tubercle, is 4^ inches, being greater than 

 the length. Another character, also contributing to the square 

 appearance of the process, is the abruptness of the junction of 

 its lower border with the side of the body, compared with the 

 gradual sloping-down of this junction in B. musculus. It should 

 be added that the transverse processes of this Megaptera have 

 been covered with cartilage, externally and half-way along the 

 upper border, while those of the B. musculus have very little of 

 the appearance of incomplete ossification. 



32. The Axis. — The anterior aspect of the body presents 

 articular surfaces and ligamentous markings corresponding to 

 those above described on the posterior surface of the atlas. 

 The ligamentous area is not sharply marked off from the low 

 odontoid elevation, but is discernible on comparing it with that 

 area on the atlas. The mesial articular surface is fully as well 

 marked off as on the atlas. It curves up to the top of the 



