164 PROFESSOR STRUTHERS. 



two laminse 2 to 3 inches apart. The recess below this, which 

 receives the lower part of the back of the mesethmoid cartilage, 

 is, in B. musculus, about 4 inches deep, and large enough to 

 receive the closed hand ; in Megaptera it is about 1 inch deep. 



15. PRENASAL SPACE. This wide gap, at and anterior to the 

 blow-holes, is much wider in Megaptera, in which it is a narrow 

 ovoid, in B. musculus elliptical. The width posteriorly, in 

 front of the nasals, is about 10 inches in both ; greatest width, 

 in Megaptera 14J inches, in B. musculus 12| inches; at the 

 narrow anterior end, in Megaptera 4 inches, in B. musculus 3J. 

 The widest part is, in Megaptera at 13 inches distal to the 

 hollow end of the nasals, 11 inches distal to the temporal fossa, 

 is at the middle of the first quarter of the beak, and just distal 

 to the coronoid process of the premaxillary. In B. musculus 

 the widest part is 17 to 18 inches distal to the hollow end of 

 the nasals, and 6 inches along the beak from the temporal fossa. 

 The widest part is, therefore, some way anterior to the distal 

 end of the blow-holes, supposing these to begin near the hollow 

 anterior border of the nasals. The distal end of the pre-nasal 

 space is better marked off in B. musculus than in Megaptera ; 

 length of the space to this part, in Megaptera 30 to 31 inches, 

 which carries it for a third of the way into the second quarter 

 of the beak ; length in B. musculus 25 inches, which carries it to 

 about the middle of the first quarter of the beak. The limit is 

 indicated by a rapid contraction to a low rounded angle. It is 

 well to notice here that in these two skulls the width of the 

 narrow inter-premaxillary space at the middle of the beak is, in 

 Megaptera, 3 inches, in B. musculus 1J. 



The vomer here, the widest part of the space, is a little deeper 

 in Megaptera, but differs considerably in width and form ; con- 

 tracting at the upper edge in B. musculus to 5f from 6| some 

 way below, while in Megaptera the upper edge is scarcely in- 

 verted, and the width is 7f inches, in adaptation to the greater 

 width of the prenasal space in Megaptera. The upper edge of 

 the vomer also differs in thickness. In Megaptera it is thickest 

 (1J inch) at the back part of the prenasal space, and continues 

 thus thick for some way within the nasal fossa ; in B. musculus 

 it is thickest (2J inches) at the middle of the prenasal space, 

 and diminishes in thickness forwards and backwards. 



