120 PROFESSOR STRUTHERS. 



dorsal in B. musculus (10 inches), in Megaptera on the 1st 

 dorsal and 7th cervical (11|), and thence, along the neck, 

 diminishes a very little forwards to the 3rd. This greater 

 width apart of the articular processes in Megaptera, by 2 inches, 

 is the more remarkable, as the bodies are narrower in it than in 

 B. musculus by fully 2 inches. From this it results that, when 

 the two sets of cervical vertebrae are viewed from below or from 

 above, the sides of the bodies are seen to be considerably in- 

 ternal to the outer edge of the articular processes in Megaptera, 

 and considerably external to them in B. musculus, affording a 

 very distinctive character. 



The above characters are seen in the articulated position. 

 The following characters of the articular processes are seen 

 when the vertebrae are laid out separately alongside each other. 

 The articular surfaces are larger and ovoid in form in Megap- 

 tera, averaging 2 inches transversely by 1 J antero-posteriorly ; 

 in B. musculus they average 2 inches transversely by f to 1 

 inch antero-posteriorly. They are larger between the axis and 

 3rd (in Megaptera 2J by 2, in B. musculus 2J by 1 J), and become 

 smaller and more irregular backwards along the series in both. 

 The difference in form is owing to the anterior processes project- 

 ing more in Megaptera ; so that in B. musculus the anterior 

 half of the ovoid is wanting, especially on the inner side, where 

 the border of the process falls gradually into continuity with the 

 anterior border of the lamina. 



In Megaptera the anterior processes, from the 3rd to the 6th 

 vertebra, are moderately convex, becoming flat on the 7th ; in 

 B. musculus the anterior processes are convex on the 3rd, 4th, 

 and 5th, flat on the 6th, concave on the 7th. Their convexity 

 on these three vertebrae in B. musculus is owing to their bending 

 down towards the transverse process ; while, behind the 5th, 

 the upper edge of the transverse process comes quite up to the 

 outer edge of the articular process. 



Considering the firm binding together of the bodies by their 

 fibro-cartilages, there can be very little movement at these 

 diarthrodial surfaces, and most of them present irregularities 

 of surface. But their greater extent in Megaptera would seem 

 to indicate more movement at the articular surfaces in it than 

 in B. musculus. 



