ar. 16, TWO SQUALODONTS FROM MARYLAND—KELLOGG. 51 
separated by a wide interval. The squamosal is firmly fixed to the 
side of the skull and internally forms part of the wall for the cranial 
cavity. The petrous portion of the squamosal fills in most of the 
tympano-periotic recess and internally is suturally united to a lateral 
wing of the basisphenoid. The posterior and outer part of the squa- 
mosal is produced downward into a thin lamina or postglenoid proc- 
ess. The glenoid surface of the squamosal is rather wide and con- 
cave from side to side. Behind the glenoid process is a blunt knob- 
like tuberosity, between which and the postglenoid process is a broad 
channel while behind this knob or rather between it and the exoc- 
cipital, there is a narrower and deeper groove or suture. The chan- 
nel on the squamosal posterior to the postglenoid process is the 
groove for the external auditory meatus, which continues its course 
upward in a deep depression on the posterior face of the postglenoid 
process of that bone, and terminating some 70 mm. above the tip of 
that process. 
In Squalodon bariensis the jugal extends from the maxillary notch to 
the antero-inferior margin of the zygomatic process of the squamosal, 
The broken edges and the roughly sculptured surface of the posterior 
margins of the lachrymals of the Maryland squalodont indicates that 
the jugal occupied a similar position. 
The horizontal ventral plates of the maxillae contribute largely to 
the formation of the roof for the oral cavity. They are separated 
from each other for most of their length by the splintlike strip of 
vomer, and are in contact only posterior to the alveolae for the last 
molars. Their surfaces are strongly convex posteriorly, and taper 
rapidly anteriorly. The maxillae are not prolonged over the ven- 
tral faces of the supraorbital processes of the frontals. The presence 
of the lachryma: makes such an extension impossible. 
In the zeuglodonts” the lachrymal occupies a position at the base 
of the rostrum and on the external margin of the supraorbital process; 
it is bounded posteriorly and internally by that process, and anteri- 
orly by the maxilla. A change in the architecture of the skull from 
the zeuglodont to the squalodont type, particularly in the rostral 
region, and the resulting constriction of the base of the rostrum and 
formation of the maxillary notches, would result in the shifting of 
the lachrymal to a more internal position. If the sutures which 
bound a small area on the right maxilla are real and not appar- 
ent, then the position of the lachryma! in the Maryland squalodont 
is in accordance with what would be expected in sueh a modifi- 
cation and its relation to the adjoining bones remains unchanged. 
Some squalodont skull in a better state of preservation may show 
that the above interpretation is incorrect, for in the Iniidae the 
7 Andrews, C. W., A descriptive catalogue of the Tertiary vertebrata of the Fayhm, Egypt. London, 
text fig. 80, p. 244, 1906. 
