150 HERPETOLOGY OF MICHIGAN. 



GKAPTE3IYS GEOGKAPHICA (La Sueur). 



MAP TURTLE. 

 (PI. VI.) 



Eniys geogyapliica, Sager, 1830, 301. 



Grapteniysi f/cographica, Agassiz, 18."57, 43V). Clark, 1002, 103, 1005, 

 110. Smith, 1870, 7. :\riles, 1861, 232. 



Description: Carapace rigid, covered with horny i)hites, de- 

 1 tressed and Aviih a distinct, slightly tubercnlated keel (much more 

 distinct in the yonng). Carapace feebly serrated behind. Plas- 

 tron large, nearly filling the opening of the carapace, immovably 

 united to it, not hinged, and distinctly notched behind. Snont not 

 ])rojecting. Cutting edge of upper jaw somewhat sinuous. 



Color of carapace dark olive, covered with a network of greenish- 

 yellow lines (occasionally uniformly dark brown above). Hexid, 

 neck, limbs and tail dark green to black Avith numerous longitudinal 

 lines of greenish yellow. A triangular yellow spot behind each 

 eye. Under side of marginal plates pale greenish or yellowish 

 with large blotches consisting of concentric lines of olive and black 

 or brown. Plastron yellow, with brownish bands (frequently ab- 

 sent in old individuals) along the sutures of the scutes. 



Habits and Habitat: The map turtle is markedly aquatic, sel- 

 dom, except during the breeding season, being found on land. In 

 southern Michigan it occurs both in lakes and rivers, but is much 

 more common in the former. According to the observation.s of 

 Garmen (1801, 237), Hay (1802a, 576), and Newman (1006, 140) 

 its food consists principally of molluscs, and very largely of the 

 heavy shelled forms of the family Viviparidae. The young feed on 

 the thiner shelled ones. Newman writes as follows: "Two methods 

 of feeding prevail. The favorite method seems to be to capture 

 the mollusc when the foot and gills are well out of the shell, to 

 bite off the soft parts and leave the hard shell. To do this the 

 final closure of the jaws must be quite sudden. If they fail to 

 secure the body of the snail in this way they adopt the crushing 

 method. The hard shell is easily crushed between the broad flat 

 jaws and the broken pieces of shell are picked out with the aid of 

 the claws. When in search of food they prowl about the bottom, 

 often underneath the dense vegetation. The heavy growth of Chara 

 or Nitella is tunneled in every direction with the passageways made 

 by foraging Graptemys." 



Hay (1802a, 576) states that "After a number had been kept for 

 a few davs in a tub there were found in it a large number of the 



