TURTLES AND TORTOISES 55 



imagined comparatively helpless in time of danger. By 

 no means are they handicapped or defenseless. The 

 rounded head with its tubular snout and fleshy lips looks 

 harmless enough. Hidden by the lips, however, are a 

 pair of mandibles remarkably keen and strong ; on many 

 specimens the mandibles form the outer border of power- 

 ful crushing processes — the alveolar surfaces of the 

 jaws; examples thus provided feed largely on mollusks. 

 Taken at a disadvantage, out of the water, the soft- 

 shelled turtles are savage fighters. The head darts at 

 an offending object like that of a snake. Large turtles 

 are dangerous : for they can amputate a man's finger — 

 possibly his hand. 



The Spiny Soft-Shelled Turtle, Trionyoc spinifer, 

 one of the American species, derives its specific name 

 from a peculiar development of the front margin of the 

 carapace; this consists, on adult individuals, of a fringe 

 of pointed, projecting tubercles. An adult has a shell 

 a foot long. Young and half-grown specimens are 

 beautifully marked with numerous black rings scattered 

 over a pale olive carapace; with both young and adult 

 the plastron is marble white. This species occurs in the 

 Mississippi River and is common in the central and 

 northern tributaries of the great water-way. In the St. 

 Lawrence River, it is found as far east as New York. 



A near ally is the Brown Soft-Shelled Turtle, T. 

 muticus, differing in the absence of tubercular spines on 

 the front margin of the carapace as well as by the more 

 obscure markings of the young. 



Both of these species are distinct from the other Amer- 

 ican soft-shelled turtles by the head markings, in the 

 shape of two pale bands that extend forward and fork 

 at the base of the proboscis. On the others, T. ferooc 

 and T. emoryi, the head markings fuse immediately in 



