4 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.61. 



The most obvious peculiarit}^ of this skull is the relatively greater 

 width of the rostrum, which, instead of being narrow and tapering, 

 as in Megaptera nodosa^ is proportionately broader at the base and 

 possibly slightly shorter. This inference is drawn from the curva- 

 ture of the rostrum as seen from a dorsal view. The preorbital and 

 postorbital portions of the supraorbital process of the frontal do 

 not over-roll the optic fossa so completely in Megaptera nodosa. In 

 the latter form the internal portion of this fossa is completely roofed 

 over by these processes. The exoccipitals are rather large and 

 rounded, while in the skull of the living humpback wdiale they are 

 somewhat compressed; their appearance in the latter indicates that 

 in the course of time they have become reduced in size and flattened 

 up against the external auditory meatus on the squamosal. The 

 descending lateral processes of the basioccipital are considerably de- 

 veloped, appearing much more conspicuous than in the living forms 

 of Megaptera. The tympanic and periotic of the living humpback 

 whale, Megaptera nodosa^ exhibit only minor modifications of the 

 type that is found in this Miocene Megaptera. 



The maxilla is a very large bone, whose dorsal plate forms the 

 greater part of the rostrum and whose ventral plate takes a promi- 

 nent part in roofing over the oral cavity. On the dorsal surface it 

 does not extend posteriorly beyond the base of the nasals. The inter- 

 nal margin of the dorsal plate is in contact with the premaxilla for 

 almost the entire length, receiving the facial process of the latter in 

 a shallow groove along the edge, though this groove is restricted to 

 the posterior end of the maxilla. 



The lateral border of the maxilla is thin and bladelike, differing 

 here but slightly in contour as well as in general proportions from 

 Megaptera nodosa. In ventral view, the posterior extremity of the 

 maxilla is observed to be very thin, ending in a sharp-edged plate. 

 Pressure exerted by the overlying beds has crushed in the center of 

 this skull, and as a result this portion of the maxilla is closely 

 appressed to the supraorbital process of the frontal. In a perfect 

 skull this part of the maxilla will no doubt be found to be very 

 much like that in a skull of Megaptera nodosa (Cat. No. 21492, 

 U.S. N.M. ) , which was figured by True." This horizontal ventral plate 

 of the maxilla is marked by shallow curved grooves for lodging the 

 bases of the blades of baleen which depend from the roof of the 

 mouth. Just anterior to the preorbital process at the lateral extremity 

 of the supraorbital there is present an indentation in the maxilla for 

 the reception of the jugal. The latter is missing in this specimen, 



" True, F. W., The whalebone whales of the western North Atlantic, Smithsonian 

 Contrib. to Knowledge, vol. 33, pi. 30, fig. 2, Washington, D. C, 1904. 



