ART. 14. THE SKULL OF MEGAPTERA MIOCAENA KELLOGG. 



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Just behind the depression for lodging the pedicle of the tympanic 

 is the facial canal, a groove running in a transverse direction, 

 which is very similar in position and shape to that of Megaptera 

 nodosa. In fact, there is a striking similarity between the entire 

 periotic of Megaptera nodosa and the same bone of this fossil. The 

 central or labyrinthic portion of the periotic which incloses the essen- 

 tial part of the auditory organ is so nearly like the corresponding 

 structure in the periotic of Megaptera nodosa that a description of 



Fig. 4. — Ventral view op left periotic of Megaptera nodosa X 1, Cat. No. 21492, 

 U.S.N.M. ; Cape Cod, Massachusetts. 



one could well apply to the other. The inferior surface of this 

 labyrinthic region is dome shaped. On the posterior surface of this 

 dome there is a slight depression formed in part by the aperture 

 of the fenestra rotundum. A rounded ridge projecting over the 

 internal margin of the facial canal marks the external boundary of 

 the labyrinthic. This same ridge in Megaptera nodosa (fig. 4) is 

 considerably flattened posteriorly as well as internally, and forms a 

 floor which extends nearly halfway across the canal. The apertures 

 for the eustachian tube and for the fenestra ovalis in this fossil are 



