_228 REPORT OF NEW JERSEY STATE MUSEUM. 
Key to the genera. 
a. Plastron not hinged, immovably joined to carapace. 
b. Alveolar surface of jaws broad. 
c. Carapace more or less keeled, scarcely depressed; upper jaw not 
notched in front; alveolar surface of jaws smooth, a deep groove in 
front; head covered with soft skin. 
d. Lower jaw with a spoon-shaped dilatation at tip. GRAPTEMYS 
dd. Lower jaw without spoon-shaped dilatation. MALACLEMYS 
cc. Carapace scarcely keeled; upper jaw notched in front; alveolar 
surface of upper jaw divided by a longitudinal ridge parallel to 
margin; head with hard skin. : PSEUDEMYS 
bb. Alveolar surface of jaws narrow. 
e. Carapace depressed, never keeled; toes strong, broadly 
webbed, and hind feet largest. CHRYSEMYS 
ee. Carapace considerably arched; feet subequal and toes nar- 
rowly webbed. cCLEMMYS 
aa. Plastron with movable transverse hinge across middle; a movable car-. 
tilaginous lateral suture unites carapace with plastron. 
f. Body depressed; plastron emarginate behind; toes well 
webbed. EMYDOIDEA 
ff. Body short and high; plastron rounded or truncate 
behind; toes scarcely webbed. DIDICLA 
Genus GRAPTEMYS Agassiz. 
The Map Turtles. 
Graptemys geographicus (Le Sueur). 
PLATE 61. 
Map Turtle. 
Carapace broad, depressed, and greatest width about */, in its 
length or opposite posterior summit of third vertebral plate. 
Anterior margin of carapace slightly emarginate. When viewed 
laterally with greatest depth apparently opposite summit of 
second vertebral plate (damaged). Median vertebral keel 
evident, most distinct on last 2 vertebral plates. Marginal 
plates broad at anterior part of carapace, narrow at sides and 
deeply concave on upper surfaces of fourth to sixth, third and 
