74 ARKIV FÖR ZOOLOGI. BAND 1. 



The difference between these two Varani with regard 

 to the structure of the palate does not only depend upon the 

 different ärran gement of the bones in the horizontal plane 

 nearer or niore remote from the median line. In correspon- 

 dence with the downward direction of the basipterygoid pro- 

 cesses of the sphenoid and the great length of the columella 

 cranii, the pterygoidea are strongly cnrved, with the convex- 

 ity downwards, in V. niloticiis, but only slightly so in V. 

 salvator. In the latter the lowermost part of the pterygoid 

 curve comes hardly more than abont 8 

 mm. below a horizontal plane laid through 

 the inferior låter al margins of the maxil- 

 lary, but in V. niloticiis about 18 mm. 

 Fig. 5. Palat.ai aspect ^he konfiguration of the palate of the two 

 of a very young Va- lizards is thus widely different and this 

 Cameroon stånds in direct conformity with the dif- 



nat. size. ferent diet of either species. 



Varanus salvator eatches and swallows, in an entire state, 

 rather large prey, and then it is snitable that the palatine 

 and pterygoid bones sit as far apart as possible, thus making 

 the passage wicler. 



In Varanus niloticiis again such an arrangement would 

 be decidedly dangerous because, if the palatine and especially 

 the pterygoid bones in that species sat far apart, it might 

 easily happen that, in the act of crushing a härd shell when 

 great muscular power had to be used, the shell or parts of 

 it slipped and became pressed in between the pterygoidea 

 and thus injured in a fatal way the weakly built anterior 

 part of the braincase. But as it is now, the stout and close 

 to each other situated palatine and pterygoid bones prevent 

 such accidents and protect the anterior braincase, the nerves 

 etc. The strong downward curve of the pterygoidea in V. 

 niloticus is also an adaptation to the shell-crushing habits of 

 this species. It effects namely, especially when the jaws 

 are shut as in tbe act of crushing, a posterior closing of the 

 mouth-cavity so that nothing can slip so easily through the 

 gullet. Thanks to this, and to the above described shape 

 of the mandible. a shell that has been taken into the mouth 

 rests there just as safely during the act of crushing as a 

 nut between the jaws of a well constructed nutcracker. 



