The first digit, or pollex, is the stoutest, and has two phalanges, the second has three, the third four, the fourth three, and the fifth two. The terminal phalanx of each of the first three digits is pointed and sheathed in a horny claw; and is also marked by a pair of prominent lateral grooves.

The Pelvic Girdle.

The pelvic girdle of the Crocodile consists of four parts, a dorsal element, the ilium, an anterior ventral element, the pubis, a posterior ventral element, the ischium, and an accessory anterior ventral element, the epipubis. All except the epipubis take part in the formation of the acetabulum, which is perforated by a prominent hole.

The ilium (fig. 49, 1) is a thick strong bone, firmly united on its inner side with the two sacral ribs. Its dorsal border is rounded, its ventral border bears posteriorly two irregular surfaces, completed by epiphyses, which are united respectively with the ischium and pubis.

The ischium (fig. 49, 2)—the largest bone of the pelvis, is somewhat contracted in the middle and expanded at either end. Its proximal end, which is formed by an epiphysis, bears two surfaces, one of which is united to the ilium, while the other forms part of the acetabulum. The anterior border is also drawn out dorsally into a strong process, which is terminated by a convex epiphysis, and is united to the pubis. The ventral end of the ischium forms a flattened blade, meeting its fellow in a median symphysis.

The pubis (fig. 49, 3) is much smaller than either the ilium or ischium; it forms a small patch of unossified cartilage, interposed between the anterior parts of the ilium and ischium.

Fig. 49. Pelvis and sacrum of an Alligator (Caiman latirostris) × ½.
(Brit. Mus.)

1. ilium.6. neural spines of sacral
2. ischium.vertebrae.
3. true pubis.7. symphysis ischii.
4. epipubis (so-called pubis).8. process bearing
5. acetabular foramen.prezygapophysis.

The epipubis (fig. 49, 4) is a large bone with a thickened proximal end, which is loosely articulated to the ischium, and a flattened expanded distal end, which is united with its fellow, and with the last pair of abdominal ribs by a large plate of cartilage. This bone is generally described as the pubis.