151 



Genus MACROCLEMYS, Gray, 



Macroclemyg, Gray, 1855, 25, 48; Macrochelys, Gray, 1855, ^5, sup., 

 64 ; Gijpochelys, Agassiz, 1857, 4, h 413 ; Macrodemmys, Boulenger, 1889, 

 84, 23. 



Carapace with three prominent keels, which persist throughout life. A 

 series of three or four supernumerary marginal scales on each side, be- 

 tween the normal marginals and the costal scutes. Plastron small, cross- 

 like, and with five pairs of scutes. Bridge narrow. Head very large, 

 covered with smooth, symmetrical plates. Orbits looking outward and 

 forward. Jaws very sti'ong and hooked. Tail with three series of tuber- 

 cles above ; the lower surface with small scales. 



Macroclemys temminokii, (Troost). 

 Alligator Snapping Turtle. 



Chelomira temminckii, Troost, 1842, 54, ii, 47, pi. 24; Macroclemys tern,' 

 minckii, Gray, 1855, 25, 49; Macrodemmys temminckii, Boulenger, 1889, 

 84, 25, with figures; Macrochelys lacertina. Cope, 1872, 1, 23; GypochelySf 

 Agassiz, 1857, 4, U 414, and ii, pi. v, figs. 23-27. 



Carapace furnished with three prominent keels which do not vanish 

 with age. Each median scute rises posteriorly into a knob, which is larg- 

 est on the hindermost vertebral scute. The lateral keel is located on the 

 upper ends of the costal scutes. The keel rises on the hinder border of 

 each scute into a knob, and the knobs on the hinder scutes are the 

 highest. Posterior border of the carapace serrated. Between the lower 

 ends of the anterior three costal scutes and the marginals occur three or 

 four supramarginals. The plastron resembles that of Chdydra serpentina. 



The head is of enormous size, broad behind, tapering rapidly to the 

 acuminate beak and snout. Beak of upper jaw projecting beyond the 

 lower, and strongly hooked, the outline of the cutting edge rising from 

 the point of the beak, then descending to the middle, and then rising to 

 the corner of the mouth. Lower jaw turned up into a strong hook. 

 Head covered with large, symmetrical plates. Neck short. Tail about 

 three-fourths the length of the carapace, furnished above with three rows 

 of low tubercles, below with rows of small scales. Color yellowish or 

 reddish brown to black. 



This species attains a great size for a fresh-water turtle. Agassiz saw 

 one alive that weighed about two hundred pounds. One of his cor- 

 respondents speaks of a skull which measured nine inches between the 

 eyes. A dry specimen that I examined in the National Museum had 

 the carapace 23 inches long and 20 wide. The head was 8 inches long 

 and 7 wide. The sternum was 16 inches long. A skull in the Indiana 



