ANA.TOMY OF MEGAPTERA LONGIMANA. 155 



The pterygoid bone, as seen here, is in B. musculus square 

 shaped, 6 inches in height, 4 in breadth, directed upwards and 

 backwards ; in Megaptera rather triangular, 4 inches in height, 

 2 to 2| inches in breadth, directed very obliquely backwards 

 and upwards. In Megaptera it is only on the right side that its 

 narrow apex is actually touched by the sickle-like part of the 

 temporal, on the left side there is an interval of f inch. In 

 Megaptera this temporal aspect of the pterygoid is marked off 

 sharply, at about a right angle, from the basilar aspect, while in 

 B. musculus the surface is continued down in a much more 

 rounded form. Here the lower division of the temporal is seen 

 to send forwards a process across the pterygoid, just below the 

 root of the orbital pedicle, in Megaptera to within about 1 inch 

 from the palate bone ; in B. musculus the interval, at the 

 narrowest, at the foramen, is 2J inches. The greater convexity 

 of the pterygoid bone here, in B. musculus, is owing to the 

 bulging of the wall of the auditory space. The pterygo- 

 temporal foramen here (admitting two fingers) is modified 

 accordingly, elliptical and oblique in Megaptera (3 inches by 

 nearly 1 inch), the pterygoid bounding only the anterior end ; 

 in B. musculus, ovoid, the pterygoid forming the inner half. 



The palate bone at this region is different. In Megaptera, 

 where the posterior and upper borders meet, it sends up a tri- 

 angular process to below the root of the orbital pedicle, pushing 

 the pterygoid outwards ; upper border of palate bone deeply 

 concave for the first six inches ; posterior border concave back- 

 wards ; foramen between palate, pterygoid, and frontal admits a 

 finger. In B. musculus the palate bone here wants all .these 

 characters; the posterior edge is very convex, indeed has a blunt 

 angle above the middle. The foramen is merged in the long 



the pedicle of the orbital cone, but in B. borealis the parietal reaches out below 

 the cone for 3 inches beyond the first inch occupied by the pterygoid, and far 

 enough forwards to cover the fissure between the two scrolls. Again, that it is 

 not the backward direction of the post-orbital bar that determines the extension 

 of the parietal upon it in Megaptera, is seen by the fact that the backward 

 direction of the bar is greater in B. borealis than in Megaptera, but the parietal 

 does not extend on the back of the bar, which is rough there, as in B. musculus, 

 though not so rough. In B. rostrata the backward direction of the bar is still 

 greater than in B. borealis, but the parietal does not reach over any part of it, 

 and the fissure between the two scrolls of the orbital cone is widely open from 

 the root. 



