AMPHIBIANS AND REPTILES. 2 
bo 
N 
Family EMY DID. 
The Pond Turtles. 
Carapace ovate, broadest behind, margin with tendency to 
flare outward, highest near middle and usually not strongly 
convex. Plastron covering whole under surface, with 12 plates, 
sometimes anterior lobe, though rarely posterior, movable on a 
transverse hinge enabling animal to completely close its shell. 
Shell covered with epidermal shields. Neck completely retractile 
within shell, and bending by a sigmoid curve in a vertical plane. 
Parietals prolonged downwards, forming suture with pterygoids, 
or separated from latter by interposition of epipterygoid. Ptery- 
goids narrow in middle, in contact on median line. No parieto- 
squamosal arch, squamosal widely separated from parietal. 
Mandible with articulary concavities. Outer border of tympanic 
cavity deeply notched. Lateral temporal arch usually present. 
Nuchal plate without well developed costiform processes. Dorsal 
vertebree and ribs immovably united and expanded into bony 
plates forming a carapace. A complete set of marginal bones, 
connected with ribs. Cervical vertebree without or with mere 
indications of transverse processes, and centrum of last cervical 
articulating with that of first dorsal. Caudal vertebrz proccelous. 
Pelvis not anchylosed to carapace and plastron. Symphyseial 
branches of pubis and ischium parallel, in contact, or narrowly 
separated from each other. Plastral bones 9. Epiplastra in 
contact with hyoplastra. Entoplastron if present oval, rhom- 
boidal, or T-shaped. Digits short or moderately elongate, with 
not more than 3 phalanges, and latter with condyles. ‘Toes 
broadly webbed in some, and scarcely webbed in others. Claws 
4 or 5. 
A large and widely distributed family. Found abont ponds, 
shores of still streams and marshes, and a few strictly terrestial. 
Though they take animal food they rarely capture active prey. 
Most will not bite except under provocation. 
