In the Meneponza alleghani the sacral trans verse processes are directed backwards, and support apophyses to which the ilia are at From the pelvis of the fossil Pterodactyle envier concludes that the forward direction of the ilia, the anterior position and pointed extremity of the pubis, and the separation of the pubic and ischiatic symphysis, ally this animal to the Saurian reptiles.
In the tailed Batrachia and Ichthycie rep tiles there is but one sacral vertebra supporting rib-like transverse apophyses which connects them to the ilia. The ilia are long and slender, and the pubes and ischia are blended together in one large, squarish, cartilaginous plate, not perforated, and loosely connected by ligament with the one of the opposite side.
In the Proleus the ilia are small, and the whole pelvis very little ossified. In the Salamander, also, the ilia are small (see fig. 110. n, a) . A cartilage, of a Y shape (d), is placed at the anterior margin of the ischio-pubic plate (b), which Duges looked upon as marsupial, but which Meckel has considered as part of the sternal elements, and which is a bifurcated pro longation of the cartilaginous ischio-pubic sym physis (c). There is also a very small obtu rator opening in the ischio-pubic plate (b). The ossification of the pelvic bones in these animals, according to Duges, takes place in the same order as in man. The pelvis of theArolot/ is, like that of the Salamander, not quite ossi fied. In the Siren, according to Cuvier, there is no vestige of a pelvis. In the Ophisaurus, accilio, and AnThisbana, there are only rudi mentary vestiges of the ilia and ischia ; and in the apodal Saurians, as in the Ophidia, a single bone only is found, under the skin near the anus. In Pseudopus anguis and Acontia are simple elongated pelvic bones, articulated by ligament to the last dorsal transverse processes. In Bryx boa a pair of elongated bones lie parallel to the rectum, free from the spinal column. They are sometimes found in several distinct pieces.
In the Sauroid reptiles the acetabula are di rected horizontally outwards, and the inflex ions of the feet are made perpendicularly to the rachis or plane of motion, the thigh being directed outwards, the knee always bent, and the body trailing. They walk on the fore and hinder legs alternately, and leap by a sudden flexion of the body.
The pelvis of the Anourous Batrachia is interesting from the changes which affect it, in their transition from the ichthycic to the quadrupedal condition.
The sacrum of the Frog (jig. A and n) is considered by Duges to he formed by the last dorsal vertebra, which closely re sembles the preceding ones, except in having very long and strong transverse processes (e), to the tips of which the ilia are moveably arti culated. In the Rana pipa and Toad, how ever, the sacrum presents evident indications of edivision into two vertebrze, there being on each side a foramen for nerves, with two prismatic and very rough transverse pro cesses. The coccyx of the Fro& is composed of two pieces (f), which, in tile abdult state, are ankylosed together and to the sacrum, and considered by some to form part of that bone. They are formed, respectively, from three points of ossification. In addition to these there is a long cylindrical terminal spinous or btyloid process (g), which is formed by a single separate ossific point, and becomes ankylosed so the other part at the adult period. This is tonsidered by some to be a second sacrum, cnd by others a coccyx. It has been supposed ay Duges to cause, by its progressive ossific development, the mortification and dropping off of the tail at the period of transition from the tadpole condition, and thus closing up the spinal canal posteriorly.
The ilia (b) are very long and cylindrical, and directed backwards,becoming ahnost horizontal in the Rana pipa. They suspend between them, by their apices, the long transverse processes and body of the sacrum, like the springs of a coach. At their opposite extremities tney are ankylosed, not only with the ischia and pubes, but with each other (h) ; and thus the acetabula, of which they form the greatest portion, are closely approximated, and the pelvic outlet assumes a V shape with the base at the sacrum and the angle at the coalesced ex tremities of the ilia. The pubes and ischia of both sides are coalesced together in an azygos osseous plate ;(c), with a central rounded crest marking the position of the symphysis (d), the pubes being the last to ossify. There is no foramen obturatorium. The posterior outlet of the Frog's pelvis looks almost directly upwards, and the anus opens, at the extremity of the coccygeal spine, upon the dorsal aspect of the animal.