VASCULAR SYSTEM. 625 



Limbs and girdles. In the shoulder-girdle, the flat 

 coracoids, with an anterior precoracoid region, articulate 

 with the sternum, which is represented by a cartilaginous 

 plate of rhomboidal shape. ( Over it projects the long limb 

 of the T-shaped episternum or interclavicle (a membrane 

 bone),, which, at the sides, is continued outwards by the 

 curved clavicles, /The remaining elements are the scapulae, 

 which are continuous with the cartilaginous supra-scapulae. 



The fore-limbs have the usual parts. In the carpus all 

 the typical nine bones are represented, and there is in 

 addition an accessory "pisiform" bone. 



In the pelvic girdle, ilium, pubis, and ischium are repre- 

 sented as usual ; there are both pubic and ischiac symphyses. 



In the tarsus the fibulare and tibiale are united, and the 

 distal row consists of only two bones. 



Nervous system. The brain consists of the usual parts. 

 The cerebellum is small and only partially overlaps the 

 fourth ventricle. In the region of the thalamus the epiphysis 

 is distinct and conspicuous, but in the adult the pineal body 

 is quite separated from it, and lies in its connective tissue 

 capsule below the skin. 



Alimentary system. Small pointed teeth are present on 

 the maxillae, premaxillae, palatines, and on the lower jaw. 

 They are fixed without sockets inside the edge of the jaw- 

 bones (pleurodont) ; in many Lacertilians they are implanted 

 along the ridge (acrodont). Salivary glands occur on the 

 floor of the mouth cavity. The narrow gullet passes 

 gradually into the muscular stomach, which again passes 

 into the coiled small intestine. Near the commencement 

 of the large intestine there is a small caecum. A voluminous 

 liver, with a gall-bladder embedded in it, and a pancreas, 

 are present as usual. 



Embedded in the mesentery below the stomach lies the 

 rounded spleen. A whitish thyroid gland lies on the ventral 

 surface of the trachea a short distance in front of the heart. 



Vascular system. The heart is completely enveloped by 

 the pericardium, and is three-chambered, consisting of two 

 thin-walled auricles and a muscular ventricle. From the 

 ventral surface of the ventricle arises the conspicuous 

 truncus arteriosus, which is formed by the bases of the 

 aortic arches, and exhibits a division into two parts. From 



