PELVIC GIRDLE (from Lat. pelris, basin; connected with Gk. 17.0e;', pcllis, pella, bowl). The pelvic girdle is that part of the vertebrate skeleton which serves for the connection of the hind limbs with the back. Among fishes there is no true girdle, although cartilaginous plates and rods lying in the mus cular tissues of the ventral side, and often connected with the pelvic fins, are regarded as rudiments of such a structure. These are best developed in dipnoid fishes, but are quite dis tinct in the sharks and rays. In the Batrachia we find a well-formed pelvic girdle made up of three parts, a dorsal ilium, an anterior ventral pubis, and a posterior ischium. Each part is made up of a pair of hones, one on each side of the body. and the iliac bones are connected with the sacral vertebra': the femur articulate. with the pelvis at a point known as `acetalilum: where the iliac, pubic. and ischiac bones meet.
In some salamanders an epipubis is present, con sisting of a slender bifurcated rod of cartilage projecting forward from the anterior edge of the pubis. In frogs and toad- the iliac bones are very long, while the isehitun and pubis are completely fused with the posterior portion of the ilium into a single piece. Among reptiles the same essential elements are present in the pelvic girdle, and the pubic and ischiac bones are united ventrally, more or less perfectly. In crocodiles there is a pro longation of the iliac bone in front of the acetabulum. In birds this prolongation is tery marked, but the relative proportion of anterior and posterior parts of the ilium differ greatly in different birds. The pubic bones of birds extend
backward parallel with the ischiae, and iu many birds fusing with them. All the parts of the pel vis of birds tend to become ankylosed, but a pubic symphysis is present only in the ostrich. and an ischiac symphysis occurs only in the rhea. Among mammals the pelvic girdle shows much variety. Both pubic and ischiac symphyses occur in mono tremes, marsupials, many rodents. insectivore-, ungulates, and carnivores. The pubic symphysis is wanting in bats and some insectivores, while the ischiac symphysis fails in many insectivores and carnivores and in the primates. In mono tremes and marsupials there are present well developed epipubic bones, known as 'marsupial' bones, though they are not concerned in any way with the marsnpium: they are associated with the muscles governing the mammary glands. A fourth element, the 'pars acetabularis,' enters into the formation of the pelvis in the crocodile, birds, and many mammals, and it often shuts the pubis out from a part in forming the acetabulum; occa sionally the ischiac bones are also excluded, as in the mole. The pelvic girdle has no fixed position throughout any class, but varies greatly accord ing to the position and function of the hind legs. A pelvis is lacking in the apodous batrachians, in all snakes (with rare exceptions), in a few lizards, and in the Sirenia and Cetacea it is either wanting or reduced to a rudimentary ilium. Consult Wiedersheim's Comparative Anatomy of Vertebrates (New York, 1SSG).