154 PROFESSOR STRUTHERS. 



in B. musculus than in Megaptera (10 inches, in Megaptera 

 7 to 8) ; the descending parieto-temporal suture curves differ- 

 ently, its outward projection in B. musculus much greater above 

 than below, in Megaptera greater below than above ; the border 

 then sweeping forwards in B. musculus to reach the level of the 

 top of the sphenoid, in Megaptera down to the level of the top 

 of the pterygoid. 



The temporal bone here is divided for some way into two 

 parts by a suture-like fissure, passing upwards and backwards. 

 The lower part, much the broadest, articulates with the ptery- 

 goid in both to about the same extent, but is smaller above 

 in B. musculus than in Megaptera (3 inches at the middle, 

 Megaptera 4J), and the fissure in B. musculus runs into the 

 angular recess of the wall and then bends sharply down. The 

 form of the upper part is determined by the relation to the 

 parietal ; in Megaptera broad above, tapering below like a 

 sickle, its point just reaching the top of the pterygoid ; in 

 B. musculus its continuation downwards is as broad as the hand, 

 reaching forwards to articulate with the pterygoid for 3 inches 

 and with the base of the sphenoid wedge. 



The sphenoid bone shows itself on the surface here in 

 B. musculus, but not in Megaptera. In B. musculus it has the 

 form of a narrow wedge, 6 inches in length ; height of base, 

 posteriorly, 1 inch, tapering forwards to a sharp point at the root 

 of the orbital cone. It articulates posteriorly with the tem- 

 poral, above with the parietal, below with the pterygoid. It 

 and the parietal are seen to end at the same point together at 

 the root of the orbital cone. The parietal is thus cut off from 

 reaching any part of the pterygoid, by the interposition of the 

 sphenoid, in contrast with the condition in Megaptera. 1 



1 The sphenoid shows itself here in B. borealis and also in B. rostrata, but 

 does not cut off the parietal from meeting the pterygoid. In B. borealis it is 

 wedge-shaped, shortened behind, so that the parietal meets the pterygoid behind 

 it for 2 inches. The temporal is thus cut off from meeting the sphenoid, but its 

 part above the fissure meets the pterygoid for 1^ inch. In B. rostrata the 

 sphenoid here is 1 inch in length on the right side, If on the left, and about 

 ^ inch in height, the wedge shortened in front so that the parietal meets the 

 pterygoid in front of the sphenoid for 1^ to If inch. The tongue-like process of 

 the temporal meets the posterior end of the sphenoid, and below that the 

 pterygoid. It might seem that the concealment, or exclusion, of this part of the 

 post-sphenoid here in Megaptera was owing to the parietal having to reach out on 



