ANATOMY OF MEGAPTERA LONGIMANA. 171 



one that is last to appear going on to the point of the maxillary, 

 seen along a course of about 5 feet. The intermediate series, 

 3 in number, issue in the roof 9 to 8 inches from the outer 

 edge, pass obliquely outwards and forwards for about 6 inches, 

 bifurcate and cease at about 3 to 4 inches from the outer edge, 

 at the first quarter of the beak. The posterior series, 3 or 4 in 

 number, issue in a line with the latter series, below the temporal 

 fossa, back to near the hinder edge of the maxillary plate. They 

 pass forwards and outwards, more curved than the intermediate 

 series (concavity backwards), bifurcate, and may then curve 

 partly backwards ; but in B. musculus (in contrast with the 

 posterior series in B. borealis) these sub-temporal grooves do 

 not at first turn backwards, although at the very back, where 

 the bone is much perforated and scaly, there may be a small 

 exception to this. They, too, have a course of about 6 inches 

 before they bifurcate and cease. 



In Megaptera this grand system of grooves is deficient except 

 the longitudinal series along the beak, and partly on the median 

 beam, being in other parts replaced by foramina only with 

 occasional short grooves. On the median beam two grooves are 

 seen to begin at the fore-end of the palato-maxillary fissure, the 

 lower one, the greatest and longest, 1 inch broad, passing down- 

 wards, and lost before the end of the first quarter of the beak is 

 reached. Three longitudinal roof-grooves appear successively 

 on the second quarter of the beak, and one runs on to the end. 

 The intermediate roof-series are represented on the first quarter 

 of the beak by apertures with very short grooves, one large 

 aperture and two or three smaller, at distances of only 4, 5, and 

 6 inches from the outer edge of the beak. In the sub-temporal 

 region, there are the foramina and scales of bones overhanging 

 shallow spaces, but not a system of grooves like that of B. 

 musculus. The cause of this deficiency of intermediate and 

 posterior roof-grooves in Megaptera is the great breadth of its 

 median beam, narrowing and filling ; up the concavity on each 

 side, and more or less roofing over what are grooves in B. 

 musculus. The position of the apertures of the intermediate 

 and posterior series, it will have been noticed, is, accordingly, 

 much farther out in Megaptera than in B. musculus. 



22. CRANIAL CAVITY. The measurements given in the table 



