ANATOMY OF MEGAPTERA LONGIMANA. 169 



differ considerably on the two sides of the same skull. In 

 Megaptera, however, they are larger, extend more into the 

 second quarter of the beak, and are on the whole more internal 

 in position than in B. musculus. In the latter they are 9 in 

 number on each side, not symmetrically placed, and are on the 

 first quarter of the beak, 5 inches within the line, except one 

 on the left side, which is on the second quarter 3 inches beyond 

 the line. In Megaptera they are. on the right side, 7 large, 

 3 very small ; on the left side, 10 large and one very small. 

 Even at the base of the frontal process they are not sym- 

 metrical ; right side, one large foramen (corresponding to the 

 infra-orbital foramen in man), directed backwards and out- 

 wards, admitting two fingers ; on left side, three foramina, each 

 admitting a finger, the upper one with the reverted direction. 

 The other foramina are too unsymmetrical to admit of indi- 

 vidual comparison. On the left side two are on the line 

 between the first and second quarters of the beak, and two are 

 respectively 3 and 5 inches into the second quarter; on the 

 right side one is on the line and one 3 inches beyond it on the 

 second quarter. The most distal one is large on the left side, 

 three times as large as on the right side. The foramina on the 

 palatal aspect are more distinctive. 



20. THE BEAK ON THE PALATAL ASPECT. The chief differ- 

 ences here are the greater breadth of the median beam and the 

 partial absence of the vascular grooves in Megaptera. The 

 measurements given in the table show also that the depth of 

 the hollow on each side of the median beam is much less on the 

 posterior part of the beak in Megaptera. The narrow keel-like 

 median beam in B. musculus gives it the appearance of greater 

 projection, but the following measurements, taken at the junc- 

 tion of the first and second quarters of the beak, will show that 

 the projection is less, and also the greater thickness of the 

 beam in Megaptera. Median beam below level of outer edge 

 of beak, in Megaptera 10 J inches, in B. musculus SJ ; breadths 

 of median beam, at two inches up, Megaptera 3f inches, B. 

 musculus 3 ; at mid-height, 6 inches up on the slope, Megaptera 

 8 inches, B. musculus 6 ; at level of outer margin of beak (12 

 inches up, on the slope, in Megaptera, in B. musculus 8J inches 

 up), Megaptera 15 inches, B. musculus 8J ; concavity taken on 



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