The femur might be easily mistaken for the humerus of a mammi ferous quadruped. Its oval head leaves the body of the bone, without being precisely separated from it, by a narrow neck. In lieu of the troehanter there is a transverse crest, but little elevated, separated from the head by a semicircular depression. The middle of the bone is delicate and round, and the lower part compressed from before backwards, widening by degrees to form the lower head, which is a transverse portion of the cylinder a little inflected backwards. Differences of modification occur in the Fresh-Water and Marine Tortoises.
The two bones of the leg aro nearly straight. The tibia is larger and nearly semicircular above, becoming again slightly larger below ; the fibula is more compressed and wider below. The first presenter a slightly concave uniform surface, the other one which is slightly convex and rhomboidal at the aatragalua. Modifications occur in the Land-Tortoises, in Clates, in Triony.r, and in the Odom's.
Bones of the Fore Foot—The differencea in the mode of progression required corresponding variations in the bones of the fore and hind feet especially. Accordingly we find that in the Chelones all the bones of the waist are flat and cut nearly square. In the first row are two bones adhering to the ulna, and in the last row five smaller ones, supporting the five bones of the metacarpus. There is besides an intermediate bone under the first ulnar bone, and upon the second and third of the last row. Cuvier observes that this would seem to correspond with that dismembered trapezoidal bone which is found in the monkeys. Lastly, there is a great aemilunar bone out of the rank, adhering to the external border of that which is above the metacarpal of the little finger. It is a true pisiform bone, although a little descended. Between that which is on the metacarpal of the thumb and the radius there is for a long time nothing but liga !near!, and one does not see the great semiluual scaphoidal which may be observed in the other sub-genera : but with age a small radial bone shows itself in this place. 'Very large individuals have also the two penultimate bones of the second row anchylosed together. The metacarpal of the thumb is short and large: the others are long and slender. The little finger has two phalanges, and is not larger than the thumb; the three others are elongated, especially the middle finger; and the whole result is a pointed hand, which has the unguial phalanx of the thumb and forefinger only armed with a claw.
In the Land-Tortoises there are but two phalanges on each finger. There are found in the carpus a great radial or semilunar scaphoidal, two ulnar bones nearly square, five bones of the second row sup porting the five metacarpals, and an intermediate bone placed between the great radial, the first cubital or ulnar, and those which carry the third and fourth metacarpal. This intermediate bone, according to
Cuvier, is often anchylosed with the semilunar acaphoidal bone. The bones of the metacarpus are even shorter than the phalanges.
In the Fresh-Water Tortoises the three mesial fingers have their three phalanges well developed ; but there are only two belonging to the thumb and the little finger. The metacarpals are rather long, and the two external oues are carried on a single bone of the carpus : nevertheless the last row consists also of five bones, because there is one, very small, externally on the side of the thumb. In the first row the ulna, in the European Tortoise at least, carries four bones— two large ones, a small intermediate one, and another small one out of the rank ; but there are other species, Testudo clausa for instance, where the two small ones do not appear. The great radial or semi lunar scaphoidal passes partially under the two uluar bones.
The Chelydea have the hand formed nearly like the Fresh-Water Tortoises, except that their radial bone is small, and re-enters towards the inside of the carpus at the aide of the bone named by Cuvier intermediate; and that the little finger has, like the three inter mediate ones, three phalanges.
The Trionyces have also the radial bone re-entering at the side of the intermediate bone. Their first three fingers have their three phalanges large, wide, and pointed to carry the claws ; the fourth has four phalanges, all rather slender ; and the last three.
Hind Feet.—Cuvier remarks that in the Cht/onia, generally, the calcaneum is without any backward prominence, so that their tarsus is flat like a carpus.
In the (Melones it is composed of six or seven bones, if tho first of the little toe be counted : two in the first row, of which the largest, nearly rhomboidal and answering equally to the tibia and fibula, is the astragalus ; the smaller, which is square and articulated only to the fibula, is the sole vestige of a calcaneum. In the second row there are four : three wedge-shaped for the metacarpals of the great toe and the two next toes, and one larger for the two last metatarsals. The bones of the metatarsus of the great and little toes are shorter than the others, and singularly wide and flat. That of the little toe however may be taken for one out of the rank of the tarsus. In this last case the little toe would have but two phalanges, otherwise three like the others. The great toe has but two. It carries a claw, and so does the next toe. The two succeeding toes have still their last phalanges rather large, although without claws, but the last has that phalanx very small.