256 NATURAL HISTORY. 



One genus of it has its plastron movable in front and a flat plated head. Its species are African 

 and Madagascan. One of them (Sternotherus sinuatus) was found by Dr. Andrew Smith in rivers 

 to the north of 25 south latitude, and where the water was very deep. They were usually observed 

 during the heat of the day lying upon rocks which projected above the surface of the water, and 

 they were so vigilant that it was almost impossible to approach them within a moderate distance. 

 They are long, rather high-bucklered creatures, the ovate shell being broadest behind. It is dark 

 greenish-brown above, and the upper part of the costal plates are livid grey, whilst the plastron is 

 pale orange, tinted with red. Its eyes are straw-yellow, and so is the head, but it is marbled with 

 greenish-yellow. 



The long-necked Pelomedusa is not uncommon, according to W. T. Blanford, in the Auseba 

 river and its tributaries in Abyssinia. But as these rivers dry up in the hot season, the creature 

 must bury itself. It has a most offensive smell. 



The Long-necked Chelodine (Chelodina lonyicollis), from the Murray region of Australia, and the 

 Oblong Chelodine (Chelodina oblongn"), from West Australia, belong to this family, which is thus 

 represented in widely separated regions. 



FAMILY III. THE TRIONYCIDES. THE MUD OR SOFT TORTOISES. 



These have the carapace flat, oval, and incompletely ossified, and therefore more or less gristly and 

 soft at the margins. The plastron, moreover, has not its pieces joined together by bone, and the 

 covering is cf skin, and not of tortoiseshell. They have a long neck, and the head is narrowed 

 in front into a kind of snout, in which are the nostrils. These Soft Tortoises are dwellers in the 

 rivers and streams, and even the arms of the sea, in the tropics of the Old and New World. They 

 swim on the surface and midway down, with equal rapidity, and pursue their prey in the water, where, 

 however, they are not without their enemies. Their colour assimilates to a certain extent with the mud, 

 so far as the carapace is concerned, but they are usually light-coloured beneath, so that they may be brown, 

 grey, or speckled above, and whitish, rosy, or bluish below. There is some ornamentation, in the form 

 of numerous yellow, brown, or black lines on each side of the carapace and on the limbs in some kinds. 

 The jaws have a skin like a lip, and the soft skin of the head has no tympanic membrane visible on 

 it. A corresponding skin without plates on it is on the limbs, which are somewhat flattened, and 

 more or less fin-like. Their extremities are webbed for swimming, and they have five digits on each, 

 but only three nails. It may be noticed that the costal plates of the carapace are short, and that the 

 marginal ossicles or plates are absent. They can draw in the neck, but not the head and limbs, within 

 the buckler. These Soft Tortoises are carnivorous and very agile, and they catch anything that is not 

 beyond a certain size which frequents their waters, young Crocodiles aiv.1 fish especially ; and, moreover, 

 they devour the eggs of these great reptiles. When they are about to seize their prey they dart out 

 their long head and neck with great rapidity, and bite and hold on fiercely, taking out a piece rather 

 than loosening their hold. The eggs are membranous, with some little shell on them, and are nume- 

 rous. The Soft Tortoises are found in the streams, great fresh-water lakes, and rivers of the hotter 

 parts of Africa, Asia, and America, but on this last continent some are found in higher latitudes in 

 the Wabash river. One common kind, the Spiny Trionyx, or Gymnopus, used to be a common 

 species from New York to Pennsylvania and the Rocky Mountains, and it has been found in the 

 Yellowstone River. It is often confounded with the Trionyx ferox, which appears to have a more 

 southern home. They have a large carapace, which floats behind and has a cartilaginous circumference, 

 and the plastron is too narrow to hide the limbs much, and there is a row of short spines along the 

 front edge of the carapace. They retreat out of the water among rocks and the stumps of trees, 

 plunging in again on the slightest alarm. They may be taken with a hook and line baited with a 

 little fish, but they are apt to jerk out their heads suddenly and to seize their captor, biting him 

 severely. Like many of the Mud Tortoises, their flesh is very nice. The females, like all others of the 

 order, seek out spots and bury their eggs, which are numerous. 



The other Soft-shelled Tortoise (Trionyx ferox, see p. 241) grows to a foot and more in length, 

 and is a voracious animal, feeding on fish and reptiles, and taking the hook, but in confinement 

 it is difficult to feed. They kill the young Alligators, and are eaten by the old ones, and reside 

 almost constantly in the water, and come out and bask in the sun. When provoked, they dart their 



