ANATOMY OF MEGAPTERA LONGIMANA. 161 



groove for 3 or 4 inches, running forwards from a IJ-inch-deep 

 median notch, no ridge proper till the nares are reached, when the 

 vomer presents a posterior edge 2 inches in height (2 on the 

 slanting edge), thickness at mid-height f inch. Length of 

 vomer from posterior end to septum of nares 14 inches, 1J more 

 at the side of the notch. The alse of the vomer in Megaptera 

 go only about a third of the way down on the sides of the great 

 sub-basilar notch, there articulating with the pterygoid by a 

 wavy antero-posterior suture ; in B. museums the alse go down to 

 within an inch of the lower end of the notch, posteriorly, by a 

 broad triangular plate covering the pterygoid. The sub-basilar 

 notch differs in form in Megaptera, besides being 2 inches 

 broader below, it is broad at the top where it is formed by the 

 vomer, and moderately convex along the sides ; in B. musculus 

 it is nearly flat at the top for about 3 inches, and has very little 

 convexity on the sides. The distance of the vomer from the 

 occipital condyle is nearly the same in both (Megaptera 5J 

 inches, B. musculus 5). The distance from the end of the 

 condyle to the posterior nares, at their septum, shows well the 

 shortness of the cranium here in Megaptera (17J inches, in B. 

 musculus 24). 



The hamular processes have been injured in Megaptera, but 

 enough remains to show a marked difference in the broad part. 

 At the notch external to the broad part, the breadth is about 

 the same (Megaptera 4 inches, B. musculus 4J), the difference 

 is in the direction and curvature of the broad part ; in 

 Megaptera, directed more inw r ards and curved inwards, giving a 

 groove on the inner surface into which three fingers may be 

 laid, one behind the other two, while in B. musculus the inner 

 surface is almost flat. This difference accords with the different 

 form of the posterior nares, the outer end of the nares being 

 narrow in Megaptera and broad in B. musculus. 



12. ANTERIOR NARIS. There is considerable difference in the 

 form of the single bony anterior naris ; in Megaptera compressed 

 vertically, in B. musculus compressed laterally. In Megaptera 

 the outer wall is bent, the whole wall forming a triangular recess 

 about 2 inches deep, and the roof is but moderately arched. 

 In B. musculus the sides are mostly vertical, rounded below, 

 and the roof is much arched, acutely so towards the middle. 



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