The river-tortoises differ in many respects from the sea-turtles, although formed like them for a purely aquatic life. In both families the extremities are complete fins, serving as oars, but the fore feet of the river-tortoises are not double the length of the hind feet, as we find in the marine chelonians; and while the latter have a short apoplectic neck, that of the river-tortoise is generally very long, and surmounted by a small and narrow head. The river-tortoises are exclusively confined to the warmer countries of the globe, and sometimes weigh as much as seventy pounds. It seems that during the night, and when they fancy themselves secure from danger, they repose upon the small river islands, or on rocks and trunks of trees that have fallen on the banks, or are drifted along by the current, and instantly plunge again into the water at the sight of man or at the least alarming noise. They are extremely voracious, and being very active swimmers, kill numbers of fish and reptiles. When they wish to seize their food or to defend themselves, they dart forwards their head and long neck with the velocity of lightning, and are said in this manner to surprise and seize even small birds that incautiously fly too near the surface of the water. They bite lustily with their sharp beak, never quitting their hold till they have fairly scooped out the morsel, so that the fishermen stand in great awe of their powerful mandibles, and generally cut off their head as soon as they are caught, rightly judging this to be the most radical means to prevent any further mischief. The Indians of the Amazons catch them either with the hook, net, or arrow. The last is the most ingenious method, and requires the most skill. The tortoise never shows its back above water, only rising to breathe, which it does by protruding its nostrils almost imperceptibly above the surface. The Indian’s keen eye perceives this, even at a considerable distance, but an arrow shot obliquely would glance off the smooth flat shell, so he shoots up into the air with such accurate judgment that the arrow falls nearly vertically upon the shell, which it penetrates, and remains securely fixed in the tortoise’s back. The head of the arrow fits loosely on to the shaft, and is connected with it by a long fine cord, carefully wound round it; as the tortoise dives they separate, the light shaft forming a float or buoy which the Indian secures, and by the attached cord draws the prize up into his canoe. In this manner almost all the tortoises sold in the small settlements on the Amazons are procured, and the little square vertical hole of the arrow-head may generally be seen in the shell. The turtles, which are likewise inhabitants of the warmer latitudes, though sometimes a strange erratic propensity or mischance will carry them as far from their usual haunts as the North Sea, have, as we all know, a far greater commercial and gastronomic value than all the rest of the tortoise tribes.[28]