ANATOMY OF MEGAPTERA LONGIMANA. 165 



16. MAXILLARY AND PREMAXILLARY BONES AT THE NASAL 

 REGION. While in B. museums the profile of these bones is here 

 almost straight on to the beak, in Megaptera they present a 

 marked fall from their posterior end for 7 or 8 inches along the 

 beak, and from this hollow the premaxillary sends up a pro- 

 cess which may be termed its coronoid process. Height of 

 process 1| inch, base about 12 inches in length, beginning 2 

 inches anterior to the peak of the nasal bones ; anterior slope of 

 process the longest, summit from 5 to 6 inches anterior to the 

 nasal peak. The height to which this process of the pre- 

 maxillary rises in the hollow is just to the level of a straight line 

 drawn from the top of the frontal process to the beak. The 

 elevation of the surface of the head, referred to with the external 

 characters, would appear to be a little anterior to this long 

 elevation, as the blow-holes, 11 inches in length, were situated 

 on the hinder slope of the elevation. 



In Megaptera the parts of the premaxillary and maxillary at 

 the side of the nasals and anterior to them, as they pass back- 

 wards are much inclined inwards, and bent with the convexity 

 inwards, while in B. musculus they have very little inclination 

 inwards. A line prolonged in the direction of the inner edge of 

 the maxillary, from the beak, goes external to the frontal end 

 of the frontal process in Megaptera 5 inches, in B. musculus 

 1 inch. The contraction from the widest part of the prenasal 

 space to between the frontal ends of the maxillaries is, in Megap- 

 tera from 14 J inches at the former place to 4 inches at the latter; 

 in B. musculus from 12J inches to 5. This, in Megaptera, is 

 partly owing to the greater width of the prenasal space, partly 

 to the greater inward encroachment of the temporal fossa at this 

 part. Width between the frontal ends of the maxillaries, outer 

 border, in Megaptera 11 inches, in B. musculus 14J. The frontal 

 process of the maxillary is broader in Megaptera, and increases 

 in breadth distally ; at the top 3 J inches, at 6 inches forwards 

 4 inches ; and then sweeps broadly outwards in its distal half as 

 the edge of the temporal fossa. 



[In B. musculus the breadth of the frontal process of the maxillary 

 at the top is 4 inches, at 12 inches forward only 2^ inches, owing to 

 the forward extension of the temporal fossa. The surface of the pro- 

 cess is very convex transversely in Megaptera ; in B. musculus it has 

 very little transverse convexity.] 



