10 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 66 



Auditory region conspicuously elevated ; orifices situated on the side or at 



the base of a nearly perpendicular wall Megaptera nodosa. 



Auditory region not conspicuously elevated ; orifices situated on an oblique 

 or nearly horizontal area. 



Internal acoustic meatus separated from cerebral orifice of facial 

 canal by a bony septum about as wide as the orifice of the canal 



Balsenoptera physalus. 



Internal acoustic meatus not separated from cerel)ral orifice of 

 facial canal by a broad bony septum. 



Cerebral orifice of facial canal and internal acoustic meatus 



opening together at bottom of deep common pit 



Balaenoptera acutorostrata. 



Cerebral orifice of facial canal and internal acoustic meatus 

 separated by a narrow, high, bony septum. • 



Fossa for stapedial muscle small, its greatest wi^lth less 



than half that of cochlear region Balaenoptera horealis. 



Fossa for stapedial muscle large, its greatest width more 

 than half that of cochlear region Sibbaldus musculus. 



COMPARISON OF THE FLORIDA SPECIMEN WITH THE JAPANESE 

 SKELETON IN THE AMERICAN MUSEUM OF NATURAL HISTORY. 



Through the kindness of the authorities of the American Museum 

 of Natural History I have been enabled to examine the Japanese 

 skeleton of Balaenoptera horcalls collected by Mr. Andrews and to 

 bring some of the smaller bones to Washington for direct compari- 

 son with our specimen. The two individuals shows numerous points 

 of difference in structure. In our present state of ignorance on the 

 subject of variation in the baleen whales I shall not, however, try to 

 draw any conclusions as to the meaning of these differences. 



Comparison of plates 1, 2, and 3 with Mr. Andrews's plates 41 

 and 42 will show the principal features of difference between the two 

 skulls. In dorsal view these are to be found in the shape of the 

 occipital shield, in the relative length and breadth of the nasal and 

 of the nasal process of the intermaxillary, in the outline of the or- 

 bital wing of the frontal and the apparently greater area of the wing 

 in the Japanese specimen as compared with that of the occipital 

 shield, and in the conspicuous swelling outward in the Florida speci- 

 men of the upper part of the parietal and squamous portion of the 

 squamosal beyond the edge of the dorsal shield. The less swollen 

 condition of the squamous portion of the squamosal in the Japanese 

 specimen is further indicated by the photographs reproduced in 

 plate 4 showing an oblique view into the temporal fossa. In lateral 

 view the rostrum appears to be deej^er in proportion to its length 

 and less curved in the Japanese specimen. The articular portion of 

 the squamosal is also deeper in proportion to its length. How far 

 these peculiarities may result from the slight difference of orientation 

 in the two photographs I am unable to saj^, but I do not believe that 

 they are all due to this cause. In ventral view the longer narrower 



