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26 united so as to be scarcely distinguishable, and incased in the common integument. They all inhabit the ocean, which they never leave except for the purpose of depositing their eggs.

The Sphargidæ, or Leatherbacks, have the bony structure of the carapace and plastron invested with a leathery skin instead of horny plates. In the young animal this is tuberculous, but in adults it is smooth, though marked with several ridges, slightly serrated, which run down through the whole length of the carapace and plastron.

The one or two species which belong to this genus compose the whole Family. Their remaining characters may be thus summed up: the carapace has seven longitudinal ridges, the plastron live; the paddles have no distinct nails; the muzzle is pointed; the jaws are of great power; the upper has a sharp tooth on each side near the tip, behind which is a deep notch, and another triangular notch in front separates the two teeth, which receives the sharp up-turned point of the lower mandible; the opening of the eyelids is almost vertical, and when closed the edge of the posterior (answering to what is ordinarily the lower) overlaps that of the anterior; the fore limbs are much more developed than the hind, and are of great length and breadth.

The species that inhabits the Mediterranean (Sphargis coriacea, .) has occasionally strayed to the shores of our own islands. Some of the specimens taken here have weighed seven hundred