ANATOMY OF MEGAPTERA LONGIMANA. 157 



seen, back to the mouth of the narrow orbital cone. The mouth 



of the cone is ovoid, in Megaptera antero-posteriorly, in B. 



musculus vertically. The meeting of the two laminae which 



close the cone below is, from the orbital margin, in Megaptera 



13 inches, in B. musculus 15. The plane of the orbital edge is 



different. Prolonged forwards the plane would, in Megaptera, 



cut off the anterior J or ^ of the beak; in B. musculus it would 



clear the beak, passing about a foot external to it. It is evident 



to the eye that the orbit has much less obliquity forwards in B. 



musculus than in Megaptera. 



8. Transverse Frontal Fossa. — At the part which may be 



so named, the supra-occipital, parietals, frontal, nasals, maxil- 



laries, and premaxillaries meet or come in near relation. The 



anterior edges of the supra-occipital and parietals ^ are seen as 



two strata lying on the frontal ; and, after an interval (the 



fossa), the frontal meets with the nasals and tnaxillaries. The 



gap is If to 2 inches long in Megaptera, in B. musculus f inch ; 



the depth, J to f inch in both. The greater length of the fossa, 



and its prolongation at the middle, in Megaptera, are mainly 



owing to the differences at the nasals, to be presently noticed, 



but the length is the same at the maxillary part as at the top 



of the nasals. Transversely, the fossa is less in Megaptera than 



in B. musculus. Here the temporal fossa in Megaptera forms a 



special inward projection (1 to 1| inch), gently triangular, as if 



the skull were pinched at this part, while in B. musculus the 



inner wall of the fossa goes straight on. The narrowest part 



between the temporal fossae is here, at the transverse frontal fossa, 



in Megaptera 10^ inches, in B. musculus 1 5 1. The great extension 



of the temporal fossae inwards in Megaptera, forwards in B. mus- 



^ The parietals are not concealed here in any of these skulls. From the usual 

 triangular thickening at the side, where tlie lateral plate gives off the transverse 

 plate, the latter is seen to pass in to the middle, where, apparently, it is fused 

 with its fellow. In Megaptera the edge of the supra-occipital is about ^ inch 

 thick, but bevelled at the very edge ; that of the parietal about ^ inch. In B. 

 musculus they are thinner, respectively about ^ and g inch. In B. borealis the 

 edge of the supra-occipital is ^ to g inch thick, that of the parietal about ^ inch, 

 and it projects for J inch or more in front of the supra-occipital. The length of 

 the fossa in B. borealis is 1 inch at the maxillaries, 1^ at the nasals. In B. rostrata, 

 too, the parietal edge is seen all the way across. A difference in Megaptera is, 

 that the supra-occipital and parietal bend down a little as they cross, in accord- 

 ance with the transverse concavity of the supra-occipital, while in these other 

 finners the edges of the supra-occipital and parietal are raised at the middle. 



