306 PEOF. n. G. SEELEX ON SIMILITUDES OF 



and above that a premaxillary ; and both agree in excluding the 

 maxillary bone from the orbit. But lizards appear almost inva- 

 riably, and like Chelonians, to admit a small portion of th.e frontal 

 into the upper orbital margin between the prefrontal and post- 

 frontal, while in Ichthyosaurs these bones meet. In Iguana and 

 many lizards, behind the orbit, completing it, is a bone which con- 

 nects the postfrontal above and the malar below with the quadrato- 

 jugal behind, and so has the relations of the postorbital in Ichthy- 

 osaurus — though, from the liberation of the quadrate bone in 

 lizards, the postfrontal and squamosal have lost their function, 

 and are of smaller size, and tlie postorbital and quadrato-jugal 

 are of different form and relations. Lizards have no supra- 

 quadrate, often have the frontal single, always have the parietal 

 single and diverging backward in a V-shape ; while in Ichthyo- 

 saurus the backward divergence is less, and almost entirely made by 

 the squamosal bones, which recurve forward round the temporal 

 fossa to meet the postfrontals above the supraquadrate and post- 

 orbital bones — an arrangement not seen in lizards. 



The foramen parietale is, in lizards, only a vertical puncture in 

 the parietal, or between the parietal and frontal bones ; in Ich- 

 thyosaurus it is an oblique canal. In Ichthyosaurus the quadrate 

 bone is seen from behind to be supported by the squamosal, opis- 

 thotic, and pterygoid ; in lizards its upper end unites with the 

 transverse bar of the exoccipital, and its lower end with the slender 

 backward prolongation of the pterygoid. 



The palate in both types is open mesially, especially in such a 

 lizard as Monitor, where the presphenoid is seen extending down 

 a similar palatal vacuity. Lizards, however, have pedicels to the 

 basisphenoid which meet the pterygoid bones ; while in Ichthyo- 

 saurus the pterygoids are more expanded, and lap round the 

 sides of the basisphenoid. In front of the long pterygoids are 

 short palatine bones in Monitor ; and between the pterygoid, pa- 

 latine, and maxillary are small transverse bones. In Ichthyosau- 

 rus both of these bones are longer than the pterygoid (supposing, 

 as was done in the comparison with crocodiles, that the palatine 

 and pterygoid bones are usually anchylosed). The vomers of 

 Monitor are long slender bones, as in Ichthyosaurus ; but the pala- 

 tine bones are not similarly prolonged between them, nor are the 

 premaxillaries external to them. 



The occipital condyle of lizards is largely made by the exocci- 

 pital bones. The teeth are never in a groove, and often differ in 



