REVISION OF MALACLEMMYS, A GENUS OF TURTLES. 15 



then flares upward ami outward a little and descends again behind; vertical and horizontal measure- 

 ments of the marginal plates above the bridge — the fifth, sixth, and seventh— approximately equal; 

 'edges of marginal plates from the sixth backward often sharp and conspicuously revolute; inguinal and 

 axillary plates may be well developed or small, or one of them may be wanting; keels of vertebral 

 plates rather low and rounded, those of the third and fourth only being at all trenchant; plates of the 

 carapace usually concentrically ridged, although in large individuals they are apt to be almost perfectlj 

 smooth. The plastron is comparatively broad, slightly notched or truncate in front, thence curving 

 outward and backward to the bridge; behind the bridge the sides of the plastron are subparallel to tin- 

 posterior margin of the femoral plate, where there is a prominent notch, and are then rather strongly 

 convergent to the ends of the anal plates, between which, on the median line, there is a rather deep 

 notch; epidermal plates of the plastron usually smooth. 



The head is large and heavy, its sides behind the eyes being mure or less swollen; nose short and 

 blunt; jaws strong and provided* with a broad horny covering; eyes somewhat prominent, but not so 

 markedly so as in the species from the Gulf of Mexico. 



The legs and feet are strong, provided with stout claws; hind feet broadly webbed. Tail short 

 and weak. 



The male differs very markedly from the female in the shape of the carapace; the margins from 

 a little behind the bridge to near the posterior end of the shell are nearly straight, so that they meet 

 at an angle instead of together forming an arc; the marginal plates from a little in front of the bridge 

 to the posterior end are nearly always strongly revolute. The head is proportionally much smaller 

 and lacks altogether the heavy, blunt appearance just described in the case of the female; the tail is 

 longer and stronger. 



The coloration is extremely variable anil offers no diagnostic characters of value. A series of 

 85 terrapin from Enterprise, North Carolina, showed the following variation: 13 females, 5 inches long 

 and under (measured on the middle line of the plastron), ranged from rather light slate-green 

 individuals, very slightly marbled with darker, to some in which the scales of the carapace were black 

 with more or less wide slate-green margins: the plastrons ranged from a rather pronounced orange 

 yellow, through honey yellow, to greenish gray; in some cases the plastrons were uniformly colored, 

 in others they were more or less blotched or clouded with dusky; the lips were white and the top of 

 the head was white or light greenish. Eight females, 5 inches long and under, had the carapace 

 entirely black and the plastron yellow r orange much blotched and clouded with black; the upper lip 

 and the top of the head were black, and the skin of the neck, legs, ami tail was gray -green with many 

 short crooked black lines and small specks. Five females, of about the same size as those just 

 mentioned, were almost perfectly intermediate in coloration, having brownish carapaces with more or 

 less strong traces of green marbling, and plastrons varying from green-gray to orange yellow, some 

 plain and others clouded. Of 8 females about 6 inches long, 2 were very light colored, the scales 

 being marked with concentric lines of greenish gray or brown on a darker background; 2 were very 

 dark brown, the others were intermediate; the plastron was yellowish gray-green, almost uniform in 

 the light colored individuals, but clouded with black in the darker colored specimens. ' >f the males 

 20 had the scales of the carapace broadly margined with greenish gray, around a center of black or 

 light brown; the lips and the top of the head were white or whitish; the plastrons were as variable as 

 in the females described above, but the dusky markings had the form of small specks rather than 

 indefinite cloudings. Eighteen males varied from uniform black to specimens in which the scales had 

 a large black center and a margin of dark greenish-gray; the top of the head was black and in all but 

 one case the lips were black; in 11 males the color was like those just described, except that the 

 tipper lip was white; in 2 males the color was dark, like those just described, but both the top of the 

 head and the upper lip were white. 



This form, although variable, can readily be recognized by its large head, smooth carapace, and 

 low dorsal ridge. From North Carolina northward it begins to intergrade with the northern form. 

 M. iTiilrata concenirwa,, and is displaced altogether before the mouth of Chesapeake Bay is reached. 

 The absence of concentric markings, usually mentioned as characteristic of the species, is apparently 

 the common condition in typical M. centraia, although now and then an individual is found which 

 shows them quite as plainly as the northern form. The usual coloration seems to he. lark brownish 

 or greenish black with a border of lighter green gray around each scale of the carapace. It is not 

 exceptional to find individuals of this species with the transverse diameters of the shell before and 

 behind the bridge nearly equal and the sides straight, the outline of the carapace thus a long oval. 



