388 



METAZOAN PHYLA 



it now seems probable that it is not an ancestral form from which other 

 lizards have sprung but rather a highly modified type which has persisted 

 from earlier times. 



419. Crocodilia. — This order contains some of the largest living 

 reptiles, the gavials of southern Asia and the caymans of South and 

 Central America reaching a length of 20 feet or more and a Philippine 

 crocodile having been captured measuring 29 feet in length. A crocodile 



(//na 



Femur 



Ilium Ischium 



Fig. 266. — Skeleton of a European turtle, Cistitdo lutaria (Marsili) 

 preparation. A, the carapace with the internal skeleton 

 The limb skeletons are inside the ribs. X %. 



From a mounted 

 B, the plastron, removed. 



and an alligator (Fig. 265) are found in southern United States. Cro- 

 codilia are lizard-like in form but the scales do not overlap, being set 

 into the thick, leathery skin, broadened, and sometimes raised to form 

 ridges. The snout is long and the nostrils are at its tip. Since the eyes 

 project from the top of the head, the animal can lie just under the 

 surface of the water with only its eyes and its nostrils exposed. The 

 eyes are covered with lids and both nostrils and ears possess valves which 

 may be closed when the animal is under water. 



There are several noteworthy details connected with the internal 

 anatomy. The teeth are conical, set in sockets, and are capable of 



