186 PROFLSSOll STRUTHEllS. 



in the position of the cerato-hyals of other Mammalia, are much 

 longer and more robust in B. musculus than in Megaptera. 

 The great horns show a difference in the presence in B. mus- 

 culus of a fusiform enlargement about the middle. This is 

 better seen on viewing them from behind than from below, as it 

 is mainly on the thickness, vertically, that the enlargement 

 occurs. As seen from the Table, in B. musculus the breadth, 

 from the middle of the horn to the outer end, diminishes by f 

 inch, the thickness by over 1 inch ; in Megaptera the breadth 

 falls by I inch, but the thickness by only | inch. The diminu- 

 tion in the thickness strikes the eye even more to the inside of 

 the fusiform enlargement in B. musculus. 



The appearance of greater up-turning of the great horns in 

 B. nuisculus (depth of the arch of the hyoid in B. musculus 7j, 

 in Megaptera 4^; inches) is mainly owing to their greater length 

 in B. musculus ; but when viewed from behind, as when laid on 

 the table, resting on the ends of the great horns, the arch in 

 B. musculus is seen to be more acute. This is seen alike on 

 the under surface, the transverse arch being considerably flatter 

 in Megaptera than in B. musculus.^ 



The stylo-hyals in this Megaptera are very like those figured 

 by Van Beneden and Gervais {loc. cit., pi. xi. fig. 7) from their 

 Megaptera Lalandii. The ends of the stylo-hyals and of the 

 horns are incompletely ossified both in Megaptera and in the B. 

 musculus. 



^ It may be noted here that, althoiii^li the hyoid of the Finners is sometimes 

 drawn and described as if the great horns have a direction backwards from the 

 body, it is not so in any of my specimens. That appearance depends on the 

 position from which they are viewed ; but if the under surface of the body is 

 taken as liorizontal, the great horns have very little, if any, direction backwards. 

 This is seen by placing the series on a table. The hyoid of Megaptera, B. mus- 

 culus, B. borealis, and B. rostrata all stand on their posterior border, and the body 

 rises vertically, or very nearly so, from the table. The great horns in B. musculus 

 have at first a slight direction backwards, and rather curve forwards again as they 

 turn up. 



This relation of the great horns to the body appears to be a character of these 

 Finners in contrast with Mysticetus. In four great liyoids iu my possession, 

 without history (picked up on the shore of the Greenland seas), but which I be- 

 lieve to be those of Mysticetus, the backward direction of the great horns is very 

 marked. When these hj'oids are placed on the table so that the body rises ver- 

 tically, the great horn and body form an arch 4| to 6 inches in height ; and when 

 tlie bone is laid on its posterior border, the body slopes forwards at an angle of 

 40° or more. 



