314 PROCEEDINGS OF THE ACADEMY OP 



a little behind the maxillary alveolus across the middle line of 

 the skull. There is no vertical orbital plate of the palatal bone ; 

 it all lies flat, and extends forward on the palate, wedge-shaped, 

 but with square termination to a point opposite the first true 

 molar. A backward spur of this bone forms with its fellow a 

 sharp median process. There are various foramina already noted. 

 The pterygoids are small claw-hammers abutting at their extremity 

 against the petrosals. 



The parietals are nearly right-angled triangles, with one side 

 of mutual apposition along the median line of the skull, another 

 transversely articulating with the frontal, and the hypothenuse 

 postero-exterior, for the mastoid suture. The back corners meet 

 the prongs of the occipital and slightly embrace the interparietal. 

 The outer corner is prolonged into a spur which attains the brim 

 of the orbit. And here the remarkable construction of the orbit 

 b} r an unusual number of bones, may be noted. Following the 

 brim of the orbit around we find zygomatic process of max- 

 illary; lachrymal; frontal; spur of parietal ; back upper corner 

 of squamosal ; front end of mastoid ; fore bulge of tympanic ; 

 zygomatic heel of squamosal; whole of malar, and so back to 

 maxillary. 



The portion of the frontal which appears on the surface of the 

 skull is keystone-shaped and straight, broad behind to articulate 

 with both parietals, narrowing anteriorly with nearly straight 

 edge, and in front irregularly tranverse to accommodate its several 

 rostral sutures. It sends a sharp spur on either hand into a 

 recess between the maxillary and intermaxillary, and each inter- 

 maxillary causes a shorter, more obtuse re-entrance ; the middle 

 part articulating with the nasals is tranverse. The orbital por- 

 tion of the frontal is a simple plate suturing behind with the 

 orbito-sphenoid and squamosal, and in front with maxillary and 

 lachrymal. The latter is of considerable extent, and much exca- 

 vated ; its edge appears upon the surface of the skull, margining 

 the back of the zygomatic process of the maxillary. 



The malar is very peculiar. In allied rodents, this bone is a 

 stout arch, and very short, in consequence of the close approxima- 

 tion of the ends of the z3^gomatic processes of both maxillaiy 

 and squamosal. But here there is, to all intents, no such squa- 

 mosal process, and that of the maxillary ends abruptly : so the 

 malar is a long bone, to complete the arch ; it is a straight rod, 



