194 DK. W. G. EIDEWOOD O]^ THE CRANIAL OSTEOLOGY OF 



is remarkably large, and has the form o£ a thin convex plate of 

 bone covering the dorsal part of tlie squamosal and the lateral 

 parts of the parietal and epiotic bones. It forms a protective 

 covering for the lateral cranial foramen. The preopercular is 

 narrow, and its forwardly directed ventral limb is short ; the 

 interopercular is small and is concealed in an external view by 

 the preopercular. 



Gircumorhital Series (fig. 5). — The nasal is a large curved 

 bone. On its dorsal surface is a broad groove v^^liich narrows 

 along its anterior surface, and terminates in a point at the 

 ventral end of the bone. The circumorbital bones proper are 

 six in number on each side. The preorbital is of moderate size, 

 the two suborbitals are comparatively large, and the three post- 

 orbitals are narrow incomplete tabes. 



Maxillary Series (fig. 5). — The gape is premaxillary ; the 

 two premaxillse are fused in the median plane, and the suture is 

 obliterated. They are comparatively short and stout, and each 

 bears about eight teeth, slender, aud bifid at the tip. The 

 maxillse are curved, toothless bones of fair size, which touch one 

 another in the median plane immediately in front of the vomer 

 and behind the mesethmoid. Each has a dorsal process which 

 projects horizontally backward, and is lodged beneath the first 

 suborbital bone. There is no surmaxilla. 



Mandibular Series (figs. 5 and 9). — The two dentaries are 

 fused in the median plane, but the suture remains visible. 

 Each carries about eleven teeth, slender, and bifid at the tip. 

 There is no clear distinction between the ectosteal, endosteal, and 

 sesamoid constituents of the articular ; neither is the angular a 

 distinct bone. 



Syojpalatine Series (fig. 9). — The union between the upper 

 edge of the hyopalatine arch and the cranium is of a very 

 intimate character ; in fact, the palatine has its mesial face so 

 closely united with the vomer, parasphenoid, and prefrontal that 

 to separate it without breaking its substance is impossible. 

 The palatine is a rectangular plate of spongy bone standing 

 vertically against the side of the front of the parasphenoid ; the 

 usual articular heads cannot be recognized. There is no 

 separate entopterygoid, and the ectopterygoid, like the palatine, 

 is edentulous. The lower edge of the ectopterygoid has a 

 uniform curve ; there is no sharp angulation. The hyo- 

 mandibular is broad, and articulates with the cranium by what 



