ORDER SQUAMATA. 1 1 37 



Kimeridgian genera are Homceosmirus^ Ardeosaurus, and Sapheo- 

 sanrus ; all of which are represented by species of small or medium 

 size. The imperfectly known Aphelosaurus, from the Permian of 

 France, was regarded by the late Professor Gervais as allied, but it 

 may indicate a distinct family, which does not belong to this group ; 

 the number of phalangeals is the same as in existing Lizards. 



Family Pleurosaurid^. — This family is typically represented 

 by PleurosauriiSy of the Kimeridgian of Bavaria, which is a medium- 

 sized Lizard characterised by the extreme elongation of the body 

 (in which there are a great number of presacral vertebrae), and the 

 long narrow skull, with slit-like nares. Anguisaurus and Acro- 

 saurus, of the same deposits, belong to this family ; but it does 

 not appear certain that they are really distinct from the type 

 genus. 



Family Telerpetid/e. — The small Telerpeton, of the Upper 

 Trias of Elgin, differs from the Homceosauridce by the presence 

 of tusk-like teeth at the extremities of both jaws, and the reduction 

 in the number of the phalangeals of the fifth digit of the pes to 

 two \ in addition to which Professor Huxley considers that the skull 

 had no postorbital bar. The one species is of small size ; and 

 although the genus agrees with the Homceosauridce, in its acrodont 

 dentition, its serial position must be regarded as provisional. 

 Saiirosternum, from the Karoo system of South Africa, is not im- 

 probably an allied genus ; although it has been referred by Sir R. 

 Owen to the Amphibian Labyrinthodonts under the name of 

 Batrachosaurus. 



Finally, it should be mentioned that Professor Cope includes in 

 the present order the genera Typothorax and Aetosaurus, which are 

 here provisionally placed, on the authority of Dr Baur, among the 

 Crocodilia. 



Order VII. Squamata. — With this order we come to the con- 

 sideration of the one represented most numerously at the present 

 day, and containing the true Lizards, the Chameleons, the extinct 

 Mosasaurians, and the Serpents. In this order the body may be 

 either short, with well-developed limbs and distinct tail (lacerti- 

 form) ; or it may be extremely elongated, without any external trace 

 of limbs, and passing gradually into the tail. As a rule, the whole 

 body and limbs are covered with overlapping horny scales ; and 

 these may be underlain by an armour of bony dermal scutes. The 

 limbs may be adapted either for walking on land, or modified into 

 paddles for swimming. In the skull the proximal end of the quad- 

 rate is more or less movably articulated ; the lower temporal arcade 

 is wanting ; the postorbital is generally fused with the postfrontal ; 

 the palate is more or less open, the pterygoids being nearly always 

 separated by an interval from one another ; and the premaxillae are 



