ART. 14. THE SKULL OF MEGAPTEEA MIOCAENA KELLOGG. 7 



OCCIPITAL CONDYLES. 



The occipital condyles, which project considerably and are borne 

 on very short condylar processes, are relatively large, equaling in 

 general proportions those of Megaj)tera nodosa. They are snbhem- 

 ispherical in outline, uniformly convex dorso-ventrally, and the in- 

 ternal margins gradually converge ventrally. The vertical diameter 

 is almost twice that of the horizontal. The external margins of the 

 condyles are set off from the exoccipitals by shallow concavities and 

 the condyles themselves slope strongly from the internal to external 

 margins. 



EXOCCIPITALS. 



The exoccipitals comprise the greater portion of the posterior end 

 of the skull. Above they are coalesced with the supraoccipital, and 

 laterally they are in contact with the posterior margins of the squa- 

 mosals, while below they are fused internally with the basioccipital. 

 The exoccipitals are large and rounded, appearing much more 

 massive than those of Megaptera nodosa. 



BASIOCCIPITAL. 



The basioccipital, on account of the knoblike lateral processes, 

 bears a close resemblance to the same element in the basicranium of 

 Rhachianectes glaucus. It is a very broad bone, with ventral surface 

 concave from side to side, and is terminated posteriorly by the paired 

 occipital condyles. The anterior margin is ankylosed to the basi- 

 sphenoid. The sutures between the basioccipital and exoccipital are 

 closed, making it very difficult to determine their boundaries. On 

 each side anteriorly there descends from this element an expanded 

 and rounded process, which serves as part of the external wall for 

 the tympano-periotic cavity. In this respect, it resembles Rhachi- 

 anectes glaucm. Anteriorly these rounded processes are in contact 

 with the vaginal processes of the internal pterygoids. 



SQUAMOSALS. 



The squamosal is exceedingly large, firmly fixed to the side of the 

 skull, and internally forms part of the wall for the cranial cavity. 

 In ventral view, the posterior and outer part of the squamosal is 

 produced downward into a great trihedral pillar. The glenoid sur- 

 face of the squamosal is wide and concave from side to side. The 

 rounded and heavy postglenoid process is directed more downward 

 than backward. Behind the glenoid surface the squamosal exhibits 

 a comparatively low, and folded-backward bladelike ridge, between 

 which and the trihedral pillar is a broad, deep channel, while be- 

 hind this ridge, or rather between it and the exoccipital, there is a 

 shallower and narrower groove concealed by the aforementioned 



