CROCODILIANS, LIZARDS, AND SNAKES. 105 



tarsale, from wliich the metatarsals radiate.' The phahiiiges number, 

 like those of the anterior foot, 2-3-4-5-3, iu ordinary Sauria, and 

 2-3-4-4-3 in Chamieleonid;e. 



2. DIGESTIVE SYSTEM. 



The alimentary canal in the Sauria is not very highly specialized into 

 distinct regions. There can always be distinguished stomach and 

 small and large intestines, the former by its muscular walls and the 

 intestines by their respectively dift'erent diameters. The stomach is 

 always simple, and is curved to the right at the pylorus, though iu 

 some of the serpentiform genera the curve is very slight. The small 

 intestine forms a sigmoid which forms a loop cephalad just distad of 

 the liver. This sigmoid is rarely simple, but is generally plicated, fre- 

 quently highly so. The large intestine may or may not be distinguished 

 into colon and rectum. The latter is constricted off at its extremity 

 from a cloaca, wiiich has common orifice with a short common genital 

 chamber immediately above it, into which enter the oviducts, usually 

 at the extremity of two papillae. 



The liver is not subdivided except at its distal border. Its form 

 differs in the different superfamilies and families, and it is more elon- 

 gate and originates further posterior to the heart in the serpentiform 

 genera in each. The gall-bladder is always situated at or within its 

 posterior border, and not at a distance from it. Sjileeu and pancreas 

 present. 



3. CIRCULATORY SYSTEM. 



The heart is not situated far posteriorly in any form, not even iu the 

 serpentiform. There is sometimes a second anterior aorta bow in front 

 of the usual aorta root. A carofis communis issuing from the right 

 aorta root. Anterior abdominal vein joining the renalis revehens near 

 the posterior border of the liver, and forming with the portal vein the 

 posterior cava. This vein passes through the liver, receiving numer- 

 ous heiiatic veins. Two anterior cardinals (jugulars) enter the sinus 

 venosus with the posterior cava. 



4. RESPIRATORY SYSTEM. 



The Sauria have two lungs, excepting the Annulati, which have but 

 one. These are situated behind and on each side of the alimentary 

 canal opposite to that portion which immediately follows the heart, 

 excepting in the Annulati, where the lung lies ventrad of the alimen- 

 tary canal for part of its length at least. Trachea with or without 



' Cuvier (Ossemens Fossiles, ed. 1836, p. 98) describes a distinct tibialo and fibulare 

 iu Chamaleon, and figures them (pi. 245, fig. 52). These are not represented by Bou- 

 lenger ( Proc. Zool. Soc, London, 1891, p. 118). They are, in fact, not distinct tarsal 

 elements, but are the epiphysis of the tibia and fibula, such as exist also in Heloderma 

 and other genera. The tihiale and lihulare are fused into a single clement as in 

 other Sauriaus. 



