104 PROFESSOR STRUTHERS. 



on the first three dorsal, sloping and convex, like the 7th 

 cervical ; from the 4th dorsal backwards, it has a slight general 

 concavity, but scarcely so on the 6th and 7th ; 4th caudal, 

 exceptional from want of development of the anterior corner. 

 Posterior border, from the second dorsal backwards, a slight 

 general concavity, but from the 6th dorsal to several of the 

 anterior lumbar very slight. The posterior border of these spines 

 might at first appear as if having a general convexity were the 

 eye to take in the upper part of the lamina, so little do the 

 posterior articular projections form a distinct angle till we get 

 well back into the lumbar region. On side view, the ends are 

 pointed on the first three dorsal, nearly flat from the 4th to the 

 llth dorsal, more rounded back to the 6th caudal, after which 

 they become less rounded. The spines of the 6th and 7th 

 caudal assume a triangular form, base above, from the prolonga- 

 tion of their posterior corner. On the 8th, 9th, and 10th the 

 spines are merely uniform decreasing ridges. 



[29. SPINOUS PROCESSES IN B. MUSCULUS.- The great expansion of 

 their ends is already referred to. In the dorsal and lumbar regions, 

 beginning at the 5th dorsal, the expanded ends are pretty close, 

 1 inch, more or less, apart, as now articulated ; and from the last 

 dorsal to the 12th lumbar, they bear marks of having been in contact. 

 The now rough facets of contact begin from 2 to 4 inches down from 

 the top of the spine behind, are mostly 3 inches in length, and ^ inch 

 in breadth, the border being specially thickened to form them. They 

 are particularly marked on each side of the 7th, and were noticed 

 there in the dissection to have a soft covering. These surfaces are 

 distinct from the unfinished edges, which, however, go down below 

 both corners twice as far as in Megaptera, thus making even further 

 anterior-posterior expansion possible. 



From the 10th dorsal to the 12th lumbar, the expansion is on the 

 posterior part of the ends, very little on the anterior part ; but on 

 and after the 1 3th lumbar, the anterior corner also expands, and, on 

 the 2nd, 3rd, and 4th caudal, is more expanded than the posterior 

 corner. The very marked expansion of the posterior part of the end, 

 as seen especially from the 13th dorsal to the 12th lumbar, is down- 

 wards as well as backwards, so that the processes come in contact 

 some way down on the one behind. This is a striking character of 

 B. musculus as compared with Megaptera. 



Another contrast between Megaptera and B. musculus is the 

 expansion, likewise backward, of the spinous process below, con- 



