6 PROCEEDINGS OF THE NATIONAL, MUSEUM. vol.61. 



The floor of the orbit can only be surmised by a comparison with 

 Megaptera nodosa^ since both jugals are wanting. 



SDPRAOCCIPITAL. 



As a whole the occipital region narrovrs toward the vertex. The 

 supraoccipital by itself forms practically the entire posterior and 

 upper part of the slaill roof, extending up to the vertex to meet the 

 frontals; in the middle line it bears a low, flattened ridge, which is 

 plainly visible even though the supraoccipital has been slightly 

 crushed anteriorly. The ridge is more conspicuous and increases in 

 prominence toward the condyles, while it stops before reaching the 

 frontals. On either side of this low ridge, the supraoccipital is 

 gently concave from side to side. The parietals are in contact 

 inferiorly with its lateral borders. 



PARIETALS. 



From a dorsal view the parietals are barely visible on the top of 

 the skull, their median parts being concealed by the protruding 

 edges of the supraoccipital. They do not enter the vertex and 

 appear in the temporal fossae as narrow wedge-shaped bones par- 

 tially limited anteriorly by the supraorbital processes of the frontals 

 and ventrally by the external pterygoids. However, the parietal 

 does override the frontal above the great supraorbital expansion of 

 this bone for some distance forward, extending beyond the vertex. 



The parietal of Megaptera iniocaena^ like that of Megaptera 

 nodosa, is in contact with the glenoid process of the squamosal, 

 the superior margin of the external pterygoid process of the alisphe- 

 noid, and overrides the supraorbital process of the frontal. 



ALISPHEXOID. 



As a result of a careful study of three skulls of Megaptera nodosa, 

 one a very old adult (Cat. No. 14409, U.S.N.M.), the second a mature 

 individual (Cat. No. 21492, U.S.N.M.), and the third a young fe- 

 male (Cat. No. 17252, U.S.N.M.), it was concluded that the ala 

 temporalis, or alisphenoid, is excluded from the temporal fossa by 

 the inferior margin of the parietal overlapping its exposed surface. 

 The examination of a skull of a young Balaenoptera in which the 

 sutures were still visible confirms this assumption to some extent. 



A close examination of the relative outlines of the various ele- 

 ments forming the internal wall of the temporal fossa of this fossil 

 whale adds additional support to this view. The sutures of the 

 small wedgelike ala temporalis, or alisphenoid, in the right temporal 

 fossa are nearly obliterated, while the same element on the left side 

 had either coalesced with the parietal or is concealed by it. 



