204 DE. W. a. KIDEWOOD ON" THE CRANIAL OSTEOLO&T OF 



The branch of the sensory tube which forms the parietal com- 

 missure arises anteriorly to the supratemporal. The supra- 

 temporal lies on the external, i. e., lateral side of the e-piotic, 

 and touches the posterior part of the parietal. On account of 

 its small size it fails to act as a cover to the large lateral 

 foramen of the cranium. 



There is a more than usually iutimate connection between the 

 preopercular and postero-superior extremity of the quadrate. 

 On the lower part of the preopercular are two sharp serrated 

 ridges, which form a posterior continuation of the two serrated 

 ridges of the mandible; and in the middle of the outer face of 

 the preopercular is a circular depression with an incomplete 

 posterior border, by which the sensory canal comes to the 

 surface of the head. In the undissected head this hole is seen 

 to be closed by a delicate, scaleless membrane, similar to that 

 which covers the posterior end of the post-temporal. The upper 

 end of the preopercular fits closely into the lateral notch that 

 occurs near the posterior end of the squamosal (fig. 13). The 

 interopercular lies some considerable distance up the inner face 

 of the preopercular. 



Circumorbital Series (fig. 12). — The bones of this series are 

 seven in number. The nasal is large, and forms the anterior 

 as well as the dorsal border of the nasal aperture. The two 

 nasal bones touch one another above the mesethmoid, and form 

 a sharp median crest. The first two of the three suborbital bones 

 are moderately large, and haye a serrated lower margin. The 

 anterior of the three gives off from its front end a process which 

 passes inward and upward, and enters into a definite articula- 

 tion with the under side of the prefrontal. A somewhat similar 

 process passes inwards from the posterior end of the second 

 suborbital, accompanied by a similar process from the anterior 

 end of the third. These processes are attached by ligament to 

 the outer surface of the ectopterygoid and entopterygoid. The 

 uppermost postorbital has the form of a tube, through which 

 passes the sensory tube on its way from the dorsal surface of the 

 squamosal and frontal (fig. 13, sc.) to the groove in the orbital 

 edge of the postorbital and suborbital bones. 



Maxillary Series (fig. 12). — Both maxilla and premaxilla 

 bear moderately long, pointed teeth on the external edge of 

 their lower border, and smaller teeth on the buccal side of these. 

 The anterior end of the maxilla lies above the premaxilla, and 



