444 PROF. W. J. SOLLAS ON A FEW SPECIES OE PLESIOSAUETJS 



termination, which takes place a considerable distance (over an inch) 

 behind the orbit. This is a marked character in several of the La- 

 certilia, particularly the Agamidse. The maxilla bears teeth at 

 least up to within 1*8 inch of its termination. 



The jugal is bounded below by the maxilla ; in front it forms the 

 posterior lower corner of the orbit ; above it joins the postorbital 

 (postfrontal), which bounds the upper posterior corner of the orbit ; 

 and behind it unites with the squamosal by a splintery suture, 

 which is 1-4 inch long, and runs almost at right angles to the length 

 of each bone. The jugal is convex outwards in front, and depressed 

 behind ; in the depression a vertical row of three oval pits (nutritive 

 foramina) separated by intervening smooth ridges is situated. At 

 the ends of the pits, which are elongated antero-posteriorly, stria? 

 appear on the surface of the bone, and are continued forwards, 

 diverging at the same time, over the otherwise smooth anterior con- 

 vexity. The external form and surface-markings thus described 

 give to the jugal such a characteristic appearance that it is easily 

 identified by them alone. 



The squamosal is a large and important bone, of which the 

 general form and relations are not quite so clearly defined as could 

 be wished. Its characteristic anterior or zygomatic process, how- 

 ever, is well displayed ; it is a thin bar of bone 1 inch broad, about 

 2\ inches long, and \ inch thick, finely striated longitudinally, the 

 stria? sweeping somewhat obliquely forwards from above down- 

 wards. 



The postorbital continues backwards from the jugal over the 

 upper edge of the zygoma for a distance of 08 inch. These three 

 bones, jugal, postorbital, and squamosal, clearly meet in a T-shaped 

 suture ; and thus Professor Huxley is undoubtedly correct in assert- 

 ing that, " contrary to what is usually stated, the postfrontal appears 



to articulate with a bone, the homologue of the squamosal 



of the Crocodile" (Quart. Journ. Geol. Soc. vol. xiv. p. 293). 



A slight extension downwards of the lower margin of the anterior 

 end of the squamosal bar, rendering its inferior outline curved con- 

 cavely, while that above is rectilinear, brings it within half an inch 

 of the posterior end of the maxilla. From that part of the jugal 

 which is exposed between the squamosal and the maxilla no bony 

 bar is produced towards the quadrate ; nor is there the slightest 

 evidence of one having ever existed, so far as this skull is concerned. 

 I feel persuaded that an inferior bony temporal arcade has never 

 been present, and that, if a quadrato -jugal occurs at all, it must be 

 as what we have called the anterior process of the squamosal, while 

 for such a view I see no evidence. 



The quadrate is clearly enough identified at its articulation with 

 the lower jaw ; but on tracing it towards the squamosal it is impos- 

 sible to say where it ends or the squamosal begins. The relations of 

 the two bones are quite obscure ; so that one cannot even tell in this 

 specimen whether what we have already termed the suprasquamosal 

 processes are the property of the bones to which we have assigned 

 them, or whether they came off from the quadrate. They appear in 



