18 PEOCEEDINGS OF THE NATIONAL. MUSEUM vol. GO 



which is in contact posteriorly with the squamosal, anteriorly with 

 the palatine, and superiorly with the parietal and frontal. 



By the backward extension of the alisphenoid (pi. 5) and its con- 

 tact with the underlying process of the basioccipital, a recess is 

 formed which completely excludes the periotic and tympanic from 

 the inner wall of the cranium. Above the descending plate or 

 falcate process of the basioccipital and near its posterior extremity 

 two foramina appear within the recess thus formed. The anterior 

 one of these pierces the bone and probably represents the compart- 

 ment for the nerves in the foramen lacerum posterius. The poste- 

 rior compartment would then be the passage for the vein in the 

 same foramen. These two compartments are not distinct in the 

 type skull and the intervening bar of bone apparently never formed. 

 The condylar foramen is situated near the posterior margin of the 

 deep incisure between the paroccipital process and the descending 

 plate of the basioccipital. Two condylar foramina are present in 

 each jugular incisure on one of the skulls. 



In the type skull the line of union between the basioccipital and 

 the basisphenoid can not be traced with certainty. The ventral sur- 

 face is concave from side to side. The descending plates or falcate 

 processes of the basioccipital are directed downward, backward, and 

 outward, and anteriorly they become closely united with those por- 

 tions of -the internal plates of the pterygoids which overlap the 

 basisphenoid. 



No attempt was made to clean the matrix from the brain case of 

 this skull and hence the position of the sutures between the bones 

 in the basicranium can not be traced. In another skull (Individual 

 2), however, the anterior surface of the basisphenoid has not united 

 with the presphenoid. The presphenoid is rodlike in the middle to 

 conform with the deep grooA'e of the vomer. 



The vomer is horizontally expanded posteriorly, sheathing the 

 basisphenoid and meeting the vaginal plates of the pterygoids along 

 its lateral margins. In front of the basisphenoid and between the 

 nasal passages the vomer becomes noticeably constricted, forming a 

 trough in which the presphenoid rests. It forms the lower portion 

 of the posterior and internal walls for each nasal passage, extending 

 upward to meet the corresponding descending plate of the ecteth- 

 moid. Between the nasal passages the vomer presents a keel which 

 anteriorly is interposed between the hamular processes of the ptery- 

 goids. In front of these processes the vomer is covered by the 

 palatines and the maxillae, but at a point 92 mm. in front of the 

 maxillary notches, the vomer again makes its appearance as a narrow 

 wedge inserted between the maxillae, and extending forward is 

 visible from a ventral view of a distance of approximately 21 T mm. 



