ANATOMY OF MEGAPTERA LONGIMANA. 149 



those of Megaptera. In like manner the comparison of the 

 actual breadths does not bring out the full proportionate 

 breadths in Megaptera, unless it is borne in mind that the 

 skull of Megaptera was only 125 inches in length and that of 

 B. musculus 145. 



3. OCCIPITAL BONE AND REGION. The foramen magnum 

 is larger in Megaptera than in B. musculus, and broader in pro- 

 portion to its height (see measurements in the Table). At the 

 upper part of the foramen the bone is thin in Megaptera (not a 

 J inch), in B. musculus very thick (2 inches). 



Condyles. The condyle is narrower in Megaptera, but the 

 two condyles together are wider in Megaptera owing to the 

 greater width of the intercondyloid space. In B. musculus the 

 lower end of the foramen magnum joins a narrow intercondyloid 

 triangle (1 inch wide) at an acute angle ; in Megaptera the 

 angle is obtuse, and the upper part of the intercondyloid space 

 is a wide triangle (3 inches wide, 2 in length). The space 

 below this is not roofed over in Megaptera, but is' so in B. 

 musculus. In Megaptera the condyles begin above by a non- 

 articular ridge 2 inches in length, beginning 1 inch above the 

 foramen ; in B. musculus the articular condyle begins at once, 

 and on a level with the top of the foramen. The condyle is 

 more bent vertically in Megaptera. The projection of the 

 condyles beyond the rest of the back of the skull l is greatest in 

 Megaptera, but their projection from the level of the bone 

 immediately external to them is 1 inch more in B. musculus 

 than in Megaptera. This will allow greater freedom and extent 

 of motion in B. musculus. 



Supra-occipital. In B. musculus there is a very well-marked 

 sharp median ridge, rising to an inch in height, ending behind 

 in a sharp diamond-shaped tuberosity, 7 inches from the foramen 

 magnum. This ridge is very obscurely marked in Megaptera, 

 which presents a broad deep median hollow along the whole 

 length of the bone, bounded on each side by the smoothly con- 

 vex side of the bone. In B. musculus these parts have irregular 

 muscular markings, and the hollow is less. The upper end of 

 the supra-occipital, at the transverse frontal fossa, is narrower 

 in Megaptera (10 inches) than in B. musculus (14 inches). 

 1 This projection does not occur at all in B. borealis or in B. rostrata. 



