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 scapula, 
which are continuous with the cartilaginous supra-scapule. 
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 maxilla, premaxille, 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 isa small cecum. 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 
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