. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 120 COMPARATIVE ANATOMY (Carinatce). The preacetabular portion of the ilium extends for- ward for a considerable distance, and a number of vertebrae belonging to other than the true sacral region become secondarily connected with the ilium {see p. 48). The acetabulum is per- forated, and the pars acetabularis (p. 119) forms a spinous process. The elements of the pelvis usually become anchylosed together. The pubis meets its fellow in the middle line only in Struthio, and the ischium only in Rhea. Mammals.—The elements
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 120 COMPARATIVE ANATOMY (Carinatce). The preacetabular portion of the ilium extends for- ward for a considerable distance, and a number of vertebrae belonging to other than the true sacral region become secondarily connected with the ilium {see p. 48). The acetabulum is per- forated, and the pars acetabularis (p. 119) forms a spinous process. The elements of the pelvis usually become anchylosed together. The pubis meets its fellow in the middle line only in Struthio, and the ischium only in Rhea. Mammals.—The elements of the pelvis here remain separated for a long time by cartilage, but later they become fused together. The pubis always takes less part in the formation of the aceta- bulum than do the other two bones, and may be more or less entirely shut out from it by an ossification of the pars acetabularis, which subsequently unites with either the ilium, ischium, or pubis (Figs. 98 and 99). This acetabular hone is especially well developed in the Mole, in which it shuts the ilium, as well as the pubis, out of the acetabulum : the latter is perforated in Mono- tremes. The angle between the axes of the ilium and sacrum is large in Ornithorhynchus, and more acute in other Mammals. The original type with both pubic and ischiatic symphyses is seen in Monotremes, Marsupials (Fig. 100), many Eodents, In- sectivores and Ungulates. In many other Insectivores, in Carnivores, and more particularly in the Primates, the ischia no longer meet below. The greatest amount of variety in the form of the pelvis. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Wiedersheim, Robert, 1848-1923; Parker, William Newton, 1857-1923. London, Macmillan
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