THE SNAPPERS AND ALLIGATOR TERRAPINS 2437 



not meet one another in the middle line, although they may be connected by some 

 small, irregular, unpaired additional shields. Further, the enormous head cannot 

 be completely retracted within the carapace, of which the anterior margin is deeply 

 excavated in order to afford it room, and the chin is provided with one or more 

 pairs of pendent wattles. With the exception of the fifth in the hind-limb, the toes 

 are furnished with claws, and the long tail is crested above. 



The alligator terrapin, or snapping turtle (Chelydra serpentina} is a 

 giant among river tortoises, and takes its name from a fancied resem- 

 blance to an alligator surmounted by a chelonian shell. It is one of 

 two species belonging to a genus characterized by the eyes being directly upward 

 and outward, so that their sockets are visible in a top view of the skull; by the tail 

 being furnished with large horny shields on its lower surface; as well as by the ab- 

 sence of the supramarginal shields found on the carapace of Temminck's snapper. 

 The carapace, which may attain a length of at least twenty inches, is characterized 

 by its rugose surface, bearing three well-marked tuberculated keels, which tend to be- 

 come smoother with advancing age; while its vertebral shields are remarkable for 

 their great width. The snout is short and pointed, with a very narrow space be- 

 tween the eyes; the skin is warty, and on the chin is developed into a pair of wat- 

 tles or barbels. In the young the tail is as long or even longer than the shell, 

 becoming relatively shorter in the adult; its upper surface having a crest of large 

 compressed tubercles, while the shields on the lower surface have been already al- 

 luded to. As in the other members of the family, the color is a uniform olive 

 brown. The alligator terrapin inhabits the rivers of North America to the eastward 

 of the Rocky mountains from Canada to Mexico, and is also found in Ecuador. A 

 second living species (C. rossignonii}, distinguished, among other features, by the 

 presence of four wattles on the chin, is met with in Guatemala and Mexico. Nearly 

 allied to this is. a third and extinct species (C. murchisont) from the Miocene rocks 

 of Baden; and as we have already seen that the mud terrapins, and probably also 

 Maw's terrapin, were represented in the Tertiary strata of Europe, it is not improb- 

 able that the Eastern Hemisphere may have been the original home of the present 

 group of families. 



Attaining considerably larger dimensions than the alligator terra- 

 Snapper P* n> Temminck's snapper (Macrodemmys temmincki} is distinguished 

 as a genus by the lateral position of the eyes, the sockets of which are 

 invisible in a front view of the skull, as well as by the presence of three or four ad- 

 ditional or supramarginal shields on the sides of the carapace, and by the under 

 surface of the tail being covered with small scales. The triangular head is propor- 

 tionately even larger than in the alligator terrapin, and the carapace has three very 

 strongly-marked longitudinal ridges. In length, the shell may measure at least a 

 couple of feet, the tail being somewhat shorter. This species inhabits North 

 America from Western Texas to Florida, extending northward to Missouri. 



Since the alligator terrapin and Temminck's snapper appear to be 

 very similar in their mode of life, their habits may be treated of col- 

 lectively. Both these tortoises frequent alike the rivers and larger swamps of the 

 United States, occurring in certain localities in enormous numbers, and most com- 



