THE SUBCLASS PARAPSIDA 267 



supported by the elongated hyoid bones. Some are subaquatic in 

 habit. The Moloch lizard, much like a "Horned Toad" in appear- 

 ance, has long dermal spines. 



Oligocene. France [Agama]. 



Pleistocene. Chlamydosaurus , Australia. 



Family Iguanidae. Arboreal, terrestrial, burrowing, or sub- 

 aquatic, reaching a length of six feet. Teeth pleurodont. No der- 

 mal ossifications. Temporal and orbital arches complete. Spines of 

 vertebrae sometimes elongate. A parietal foramen. Zygosphenes 

 sometimes present. Herbivorous and insectivorous. 



About three hundi'ed species and fifty genera are known of this 

 family, almost exclusively American in distribution, including our 

 largest and some of our most common lizards, — the Basilisc lizards. 

 Iguanas, "Horned Toads," etc. The large Galapagos lizard, Ambly- 

 rhynchus, is a noteworthy herbivorous, aquatic form that seeks its 

 food in shallow water, returning to the land for safety when pressed 

 by enemies; perhaps one of the ways in which terrestrial reptiles 

 acquired water habits. 



Eocene. Iguanavus Marsh, North America. Proiguana Filhol, 

 France. 



Family Anguinidae. With well-developed, pentadactyl hmbs, or 

 limbs vestigial. Body covered with dermal ossicles beneath corneous 

 scales. Temporal opening roofed over by dermal bones. Teeth 

 pleurodont. A parietal foramen. 



This family, common to Europe and America, comprises about 

 fifty species. Most noteworthy are the "Glass Snakes" and the 

 "Slow Worms," with vestigial limbs or wholly without them. 



Miocene. Anguis, Diploglossus, France. 



Family Helodermatidae. Poisonous, terrestrial lizards with 

 grooved, slender, pleurodont teeth. A postorbital but no temporal 

 arch, the squamosal absent; prefrontal and postfronto-orbital in 

 contact over orbits. Parietals and frontals fused. No parietal fo- 

 ramen. Upper surface of body and skull more or less covered by 

 dermal ossicles. An ossified, subfrontal, rhinencephalic chamber. 

 Quadrupedal. 



But one genus and two species of this family are known, the fa- 



