ANATOMY OF MEGAPTERA LONGIMANA. 167 



Megaptera than in B. musculus (45 and 48 inches), and at the 

 end of the first quarter (Megaptera 33 J, B. musculus 36) ; but 

 after this the breadth is greatest in Megaptera, at the middle 

 Megaptera 27 J, B. musculus 27; at the end of the third quar- 

 ter, Megaptera 19 J, B. musculus 17. The measurements given 

 in the table show to what extent these breadths belong to the 

 maxillary, premaxillary, or to the mesial space. At the base, 

 and at the end of the first quarter, the prenasal space and the 

 direction of the surface of the premaxillary affect the measure- 

 ments. At the middle of the beak the greater breadth in 

 Megaptera is owing to the mesial space, which is nearly 2 inches 

 wider than in B. musculus, but at the end of the third quarter 

 nearly half of the decidedly greater breadth in Megaptera than 

 in B. musculus is owing to the maxillary. Viewed from above, 

 the breadth of the beak in Megaptera has very much the appear- 

 ance of being less in front of the base than at the end of the 

 first fourth, but the form deceives the eye ; the narrowest part 

 is behind the middle of the first quarter (33 inches), and from 

 that part the breadth diminishes forwards. 



The fall of the upper surface of the beak to its outer edge is 

 on the posterior half, greatest in B. musculus, on the anterior 

 half greatest in Megaptera. The amount of the fall at the 

 base, at the end of the first quarter, at the middle, and at the 

 end of the third quarter, respectively, is, in inches, in Megap- 

 tera 10, 4J, 3|, 2| ; in B. musculus 10 J, 5, 3, If. This greater 

 slope of the distal half of the beak in Megaptera is manifest to 

 the eye. The surface is less convex transversely in B. mus- 

 culus, giving the distal half of the beak a very flat appearance 

 in B. musculus. In Megaptera the maxillary is convex trans- 

 versely about the middle, with a slight concavity internal to 

 this, but the chief transverse convexity is on the premaxillary, 

 which is so great, on the second quarter and on part of the 

 third quarter, that the highest part of the beak is on the sur- 

 face, not at the inner border, as it is along the distal half of the 

 beak. The line of articulation between the maxillary and pre- 

 maxillary is, in Megaptera concave outwards on the two middle 

 quarters (concavity 1^ inch deep), convex outwards on the 

 distal quarter. In B. musculus these undulations are much 

 more gentle, the concavity of the first about f inch deep. 



