150 PROFESSOR STRUTHERS. 



The ex-occipitals are not so broad in Megaptera as in B. 

 musculus, and are smoothly convex in both directions from a 

 little way external to the condyles ; the most projecting part 

 is at the junction of the outer and middle thirds, from which 

 the surface falls smoothly to the outer edge, without any par- 

 occipital ridge. In B. musculus there is a transverse depres- 

 sion along the outer half, the surface more sharply bent verti- 

 cally and flatter transversely; the most projecting part is at 

 the extreme outer edge, rising into a prominent par-occipital 

 ridge. The ex-occipitals descend below the level of the con- 

 dyles more in Megaptera (3| inches) than in B. musculus 

 (2 inches). 



Basi-occipital. — In Megaptera the sub-occipital notch be- 

 tween the inner walls of the ear-bone spaces, and receiving the 

 vomer, is wider in Megaptera (15 inches, in B. musculus 13). 

 This part will be further noticed with the vomer. External to 

 this, the sharp triangular fissure in the occipital margin, open- 

 ing into the ear-bone space, is much deeper and wider in 

 Megaptera (depth 4 to 5 inches in Megaptera, in B. musculus 

 2 inches). 



Occipital Plate of the Temporal Bone. — This plate, in its 

 form and great size, presents one of the most striking differences 

 between Megaptera and B. musculus. Its outer and lower part 

 (post-mandibular ])rocess) has the glenoid fossa in front for the 

 support of the condyle of the mandible. It is much larger and 

 more square-shaped in Megaptera. The measurements are, 

 along lower border, sloping downwards and outwards, in Megap- 

 tera 13 inches, in B. musculus 12; transversely at about the 

 middle, outer border moderately concave, Megaptera 15, B. 

 musculus 12 ; transversely at posterior angle of temporal fossa, 

 in Megaptera 18|, in B. musculus 13 A ; antero-posteriorly, at 

 inner part, in Megaptera 18, in B. musculus 14| ; at outer 

 border, in Megaptera 23 (going as far as the articulation with 

 the frontal bone and to four inches from the anterior end of the 

 zygoma), in B. musculus, as seen from behind, also about 23, but 

 indefinite from the rounding off into the long zygoma, and about 

 11 inches from the anterior end of the zygoma. The outward 

 slope of this border is such that its upper part is more external 

 than its lower, in Megaptera 7 inches, in B. musculus 2i. The 



