. Water reptiles of the past and present . ulna,the capitellum and trochlea. A little aboveeach of these condyles there is usually, onone side or the other or on both, a foramenor hole for the passage of arteries or on the inner side, which is character-istic of all early reptiles and of manymammals, is called the entepicondylarforamen; that on the outer side, the ectepi-condylar foramen; the latter is present inthe lizards, and both are found in thetuatera and some of the early radius and ulna are always distinctbones in reptiles, and always freely mov-able on each ot
. Water reptiles of the past and present . ulna,the capitellum and trochlea. A little aboveeach of these condyles there is usually, onone side or the other or on both, a foramenor hole for the passage of arteries or on the inner side, which is character-istic of all early reptiles and of manymammals, is called the entepicondylarforamen; that on the outer side, the ectepi-condylar foramen; the latter is present inthe lizards, and both are found in thetuatera and some of the early radius and ulna are always distinctbones in reptiles, and always freely mov-able on each other; they are usually shorterthan the humerus, but in some springingand climbing reptiles they are quite as long. The carpus or wrist of reptiles consists primitively of elevendistinct, irregularly shaped bones, which articulate more or lessclosely with each other in three rows. Those of the first row, alltrue carpals, are known usually as the radiale, intermedium, ulnare,and pisiform, corresponding quite with the bones of the human wrist. Fig. 2i.—Anterior ex tremity of Ophiacodon. THE SKELETON OF REPTILES 39 known as the scaphoid, lunar, cuneiform, and pisiform. The secondrow has but two bones, on the radial side, known as the centralia;while the third row has a bone to correspond to each of the meta-carpals, five in number, and collectively known as the or indeed all of these bones may be either absent or unossified,that is, remaining through life as nodules of cartilage. Seldom,however, are there less than nine bones in the carpus of reptiles. The metacarpals, like the digits, primitively were five in number,and seldom are there less, though the fifth is sometimes lost, andrarely also the first. They are more or less elongate bones, increas-ing in length from the first to the fourth, with the fifth usuallyshorter. The first and the fifth are usually more freely movableon the wrist than are the other three. The number of joints or phalanges in the fingers of
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