REPTILIA. 
SYNOPSIS OF ORDERS. 
A. Cloacal aperture transverse; penis double; dorsal verte- 
brae movable upon one another and ribs upon them; teeth 
present; lungs free; limbs when fully developed, with free 
digits; heart trilocular. v : . 
a. Rami of lower j$j&’ loosely united in front by ligament 
and muscle, attached behind to a movable quadrate 
bone, which in turn is connected with a movable squa- 
mosal; palatine united to pterygoid only; no pectoral 
arch or urinary bladder; no eyelids or tympanic 
cavity Ophidia. 
b. Rami of jaw more firmly united; no movable squamosal; 
anterior ends of palatines united to maxillae and 
vomers; pectoral arch and urinary bladder present; 
usually with movable eyelids and a tympanic cavity. 
Lacertilia. 
B. Cloacal aperture round or longitudinal; penis simple. 
a. A dorsal shield or carapace present, composed of the 
much-flattened spinous processes of the dorsal vertebrae, 
and the greatly expanded ribs, which are united to 
superficial bony plates ; ribs and dorsal vertebrae 
immovable; all vertebrae without transverse processes; 
an abdominal plate or plastron; pectoral and pelvic 
arches within shield; scapula and precoracoid anchy- 
losed ; quadrate firmly united to skull ; heart trilocular; 
lungs fixed against inner periosteum of carapace; no 
true teeth; urinary bladder present Testudinata. 
b. No carapace or plastron ; anterior dorsal vertebrae with 
elongated and divided transverse processes; teeth in 
sockets; lungs free; four well-developed limbs; heart 
quadrilocular ; rami of lower jaw united by suture; 
quadrate immovably fixed to skull; no urinary bladder; 
movable eyelids, and rudimentary external ear. 
Crocodilia. 
