The Terrapins 



protruding so abruptly from the shell as to produce a bluntly 

 serrated margin to the curve of the back. The species have 

 very large and extensively webbed hind feet. The claws of the 

 front feet do not exhibit the extensive development to be noted 

 with the species of the preceding genus. 



From Chrysemys, this genus is technically separated by the 

 structure, in the latter, of the inner margin of the jaws, which, im- 

 mediately within the sharp edge of the mandibles, are provided 

 with very broad and flat crushing surfaces. Upon an examination 

 of these crushing surfaces, theory would point to a food consist- 

 ing of molluscs. Such is actually the case. Most of these tur- 

 tles have been found to feed largely upon small species of snails. 



Male and female specimens differ considerably in size, the 

 females being much larger and with proportionately larger heads 

 than the males. 



The tail of male speciments is long and thick, proportion- 

 ately longer than with any species of Chrysemys. 



Following is a key to the species of Malacodemniys: 



Shell broad and flat with all the species; not globular: rising 

 to rather a sharp apex which is surmounted by a broken keel, rep- 

 resented by high, ridge-like nodules. 



a. Shell smooth, with a dull lustre. 



*KeeI moderately developed, not rising in the form of 

 tubercles. 

 Olive, sometimes with black blotches. 

 A net-work of fine, yellow lines. 



GEOGRAPHIC TERRAPIN, M. geographicd 

 Distribution. — Mississippi Valley and western por- 

 tions of Atlantic states. 

 **Keel rising in the form of tubercles, giving line of 

 back a serrated appearance. 



Olive, with large, round, black blotches. 

 No yellow net-work. Head with narrow, yellow 

 lines and a wider, yellow crescent behind eye. 



lesueur's terrapin, M. lesueurii. 

 Distribution. — Mississippi Valley. 

 Carapace like preceding. A large yellow spot 

 behind eye. A narrow line from above eye ; short- 

 er lines beneath. kohn's terrapin, M. kohnii. 

 Distribution. — Lower Mississippi Valley. 

 Pale, olive; no large blotches; marginal shields 

 marked with yellow. Space between the eyes 

 with a broad, yellow figure, splitting into bands 

 behind the eyes. baur's terrapin, M. pulchra. 

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