50 PROCEEDINGS OF THE NATIONAL MUSEUM. you. 62. 
which are furnished by the descending lateral wings of the basi- 
sphenoid, and the squamosal. <A large and well-marked groove which 
originates within the cranial cavity follows down the external face of 
the descending plate of the basioccipital along its line of union with 
the exoccipital. This is interpreted to be the posterior lacerated 
foramen. Condylar foramina are present on either side of the basi- 
occipital. 
The basisphenoid is flat in comparison to the basioccipital and the 
anterior margin was concealed to some extent by the vomer and the 
vaginal plates of the internal pterygoids. If the sutures have been 
correctly ascertained the basisphenoid does not enter into the for- 
mation of the lateral descending plates of the basioccipital except at 
the base and then only in front of the line of contact between these 
two elements. 
The presphenoid is permanently separated from the basisphenoid 
by an open transverse suture, apparently paralleling in this respect 
Squalodon zitteli.4 This region in the skull of Squalodon bariensis is 
concealed by the vomer and the adjoining vaginal processes of the 
internal pterygoids. The posterior end of the vomer as preserved in 
the Maryland squalodont commences 112 mm. in advance of the 
foramen magnum. As remarked above, the imperfect state of preser- 
vation of this portion of the skull prevents accurate description. 
However, the free ends of the palatine plates of the maxillae show 
that the palatines were suturally united to the former, and that they 
did not extend as far forward as the maxillary notches. On the other 
hand Lortet’s figure of Squalodon bariensis suggests that the palatines 
may have terminated in front of the maxillary notches. 
The vomer first makes its appearance on the ventral surface of the 
skull as a splintlike bone inserted between the palatine plates of the 
maxillae, commencing near the alveolae for the second molars and 
disappearing on a line with the seventh as in Squalodon zitteli. It 
again makes its appearance posterior to the internal openings of the 
nasal passages. In order to insure a correct contact between the two 
major portions of the matrix during the preparation of this specimen 
it was necessary to fill in this portion of the skull with plaster of Paris, 
and no attempt was afterwards made to restore these passages to 
their natural appearance. The vomer is characterized by a well- 
developed carina, though this, presumably, is merely a posterior con- 
tinuation of the ascending plates that sheath the internal walls of the 
nasal passages inferiorly. 
The squamosals are produced outward and the zygomatic processes 
thus formed do not closely approach the posterior part of the supra- 
orbital processes of the frontals as in Squalodon bariensis, but are 
74 Zittel, K. von, Palaeontographica, Stuttgart, vol. 24, pl. 35, fig. 3, 1876-77. 
