COLD-BLOODED VERTEBRATA 



3»S 



Botalli and ductus arteriosus 



that are persistent in the Common Newt, is also complete ; 

 in other cases both ductus 

 remain open, and so on. 



In the kidneys of the 

 newt there is a distinction 

 between the so-called meso- 

 and metanephros, which 

 recalls the condition of 

 these organs in the dogfish. 



Reptiles 1 resemble Am- 

 Reptma. Phibians in 



being cold- 

 blooded, lung - breathing, 

 pentadactyle vertebrates, 

 but they have an exo- 

 skeleton of horny scales, 

 with sometimes also bony 

 plates, twelve cranial 

 nerves, 2 stout, usually 

 chalky shells to their eggs, 

 no larvae, and in their em- 

 bryos amnion and allan- 

 tois, which we have already 

 mentioned (see p. 506). 

 They comprise Turtles, 

 Crocodiles, Snakes, Lizards, 

 and the Tuatara, a little 

 lizard-like animal found in 

 New Zealand. Thus when 

 popular speech calls frogs, 

 toads, and newts " reptiles " 

 it is not strictly correct, 

 though Amphibians may 

 justly be said to be more 



Fig. 278.— The skull of Capito- 



saurus nasutus, one of the 



Stegocephali. — From Rey- 

 nolds, after von Zittel. 



i, Premaxilla ; 2, nasal; 3, maxilla; 4, 

 anterior nares ; 5, frontal ; 6, pre- 

 frontal {or lachrymal) ; 7, lachrymal 

 {or adlachrymal) ; 8, jugal ; 9, orbit ; 

 10, parietal ; n, postfrontal ; 12, post- 

 orbital ; 13, interparietal foramen ; 

 T4, squamosal {or supratemporal) ; r5, 

 supratemporal {or prosquamosal) ; 16, 

 quadratojugal ; 17, quadrate; 18, 

 epiotic {or tabulare) ; 19, dermal supra- 

 occipital {or postparietal) ; 20, exoc- 

 cipital ; 2r, foramen magnum. 



The sheet of membrane bones which 

 forms the roof of this skull is a special 

 development of the armour of bony scales 

 which is found on other parts of the body 

 of Stegocephali. It is not only the roof of 

 the cranium, but stretches over the space 



nparlv ntin rn rpnrilpc than Detween tne cranium and the upper jaw 

 nearly aKin tO repilieS man ( p alato-pterygo-quadrate bar). In most 



to any 

 animals. 



other class of 



other bony skulls, gaps (the fossae, p. 386) 

 appear between the bones of this dermal 

 sheet. 



1 The student who wishes to make a systematic study of the anatomy 

 of a reptile will find assistance, with figures, in the practical direc- 

 tions on p. 578. 



2 Except in snakes. 



