380 METAZOAN PHYLA 



2. Rhynchocephalia (nn ko se fa' li a; G., rhynchos, snout, and 

 kephale, head). — One living type, a lizard-like animal found only in 

 New Zealand. 



3. Crocodilia (krok o dil' i a; G., krokodeilos, crocodile). — Crocodiles 

 and alligators. 



4. Testudinata (tes tti di na' ta; L., testudinatus, like a tortoise). — ■ 

 Turtles and tortoises. 



412. Internal Structure. — The heart of a reptile consists of two 

 auricles and a double ventricle (Fig. 258^), the latter being divided by a 

 septum which, however, is perforated, except in Crocodilia. The blood 

 from the veins enters the right auricle, passes into the right ventricle 

 and thence to the lungs. From the lungs it is returned to the left 

 auricle, goes to the left ventricle, and out through the two aortic arches 

 to the arteries. The blood in the two ventricles mingles to a certain 

 extent, and so mixed blood is sent out over the body. In the Crocodilia 

 (Fig. 258 B), where the ventricles are quite separate and the left aortic 

 arch as well as the pulmonary artery arises from the right ventricle, a 

 communication between the two aortic arches permits mixing of the 

 arterial and venous blood. Renal-portal and hepatic-portal systems are 

 both present, the latter being better developed than in the amphibians. 



The lungs of reptiles are rendered more complex than those of the 

 amphibians by repeated divisions of the bronchi and an increase in the 

 number of the alveoli. This increases considerably the surface through 

 which respiration is carried on. 



The brains of reptiles (Fig. 259) show an advance over those of the 

 amphibians in the better development of the cerebral hemispheres and 

 of the cerebellum. The greatest advance, however, is in the appearance 

 of a cerebral cortex. Here, as a result of the multiplication of the nerve 

 cells and their regular arrangement, the roof of the cerebrum is divided 

 into an outer gray layer and an inner white one. The cells in the gray 

 matter are arranged in distinct groups or areas corresponding to the 

 particular activities which they control. Such a brain roof is called a 

 cortex. 



In the reptiles the organs of sight and hearing are generally well 

 developed, as are also to a lesser degree those of taste and smell, while the 

 skin over various parts of the body is very sensitive to touch. There 

 is usually a middle ear, with a tympanic membrane, a eustachian tube, 

 and a columella. In the chameleons and snakes the tympanic membrane 

 is absent; in the turtles it is on the surface of the body; and in the lizards 

 and crocodiles it is at the bottom of a pit, which may be considered the 

 beginning of an outer ear. 



413. Squamata. — This order is characterized by a typical scaly 

 covering which is shed periodically. In the case of snakes it is cast off 

 complete and at one time, but in the lizards it is stripped off in shreds 



