REPTILIA 



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the lower jaw fitting into a socket. The gavial has a decidedly long 

 and pointed snout and the first and fourth lower teeth bite into 

 grooves in the upper jaw. 



Voice. — Snakes and lizards have no vocal cords, but hiss through 

 the nose. Crocodilia roar and the tortoise of the Galapagos Islands 

 bellows. 



Circulatory System. — xAll Reptilia have a four-chambered heart, 

 but with the exception of the Crocodilia the ventricular septum is 

 perforated. The red corpuscles of snake blood are 11 microns long, 

 approximately the same as in frog blood, but those of the lizard are 

 about 16 microns in length. 



Excretory System. — The kidneys are not always symmetrical in 

 Reptiles, in the Snakes for example being elongated and band-like. 

 The kidneys of Lizards are fused in the mid-line. A urinary bladder 

 (usually bi-lobed) is found in Lizards and Chelonians, but is lacking 

 in Snakes and Crocodiles. The urine is rich in salts and solidifies 

 quickly on reaching the air as in the case of birds. 



Reproductive System. — Fertilization is internal in the Reptilia, 

 which have either a bifid or a median solid penis. Many Lizards 

 and the majority of Snakes are viviparous but the Crocodilia and 

 Chelonia are oviparous. 



Care of the Young. — Crocodilia and Chelonia deposit their eggs 

 in nests of sand or twigs and grass, and return to them periodically. 

 The female python protects her eggs by coiling around them, her 

 temperature rising several degrees during the process to promote 

 hatching. 



Nervous System and Sense Organs. — In the Reptilia the brain 

 has distinctly advanced from the amphibian type. The cerebral 

 hemispheres have developed greatly but the cerebellum remains 

 small. The eyes are large and the ears well developed, except in the 

 Snakes where a middle-ear is absent. Tactile, olfactory and 

 gustatory senses are well developed. The Turtle is surprisingly 

 sensitive to taps on its shell. 



Rattle of the Rattlesnake. — Several species of snakes, including 

 the bushmaster and the copperhead, have a large horny spine at 

 the base of the tail. In the rattlesnake after the first year, three 

 moults occur annually and at each moult a new rattle is formed. 

 Considering the first ring to represent the first year, the age of a 

 rattlesnake may be determined by allowing three rings for each 

 year. The possibility of accidental loss of a segment or two must 

 of course be considered. 



