SYNOPSIS OF THE PRINCIPAL GROUPS. 118 
cles; teeth firmly attached to the jaws (ex- 
tinct). 
Rhynchocephala. Body lizard-like; verte- 
bree amphiccelous; ribs with uncinate pro- 
cesses; the sternal ribs articulate to the 
vertebral ribs, and abdominal ribs are present ; 
quadrate bone anchylosed to the skull: teeth 
on the palatine bones. 
Lacertilia. ‘Skin generally with scales; dor- 
sal vertebre usually proccelous, rarely am- 
phiccelous ; a pectoral arch; limbs present or 
absent ; teeth anchylosed to the jaws. 
Ophidia. Body elongated, and covered with 
scales ; dorsal vertebree proccelous; no pectoral 
arch; limbs absent, or rudimentary ; teeth 
anchylosed to the jaws. 
Crocodilia. Body with bony plates or scutes : 
teeth in distinct sockets; heart with two 
auricles and two ventricles, but the pulmonary 
and systemic aortas are connected. 
Anomodontia. Jaws sheathed in horn ; limbs 
_ strong, fitted for walking (extinct). 
Pterosauria. Jaws with teeth in sockets; 
sternum broad; hand of four digits, the outer 
of which is elongated, for carrying a mem- 
brane for flying (extinct). 
Dinosauria. Teeth in sockets; feet with 
claws ; fore limbs generally small; hind limbs 
and pelvis bird-like (extinct). 
Theriodontia. Jaws with incisors, canines, 
and molars; the canines very large (extinct). 
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