. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. DIVISIONS OF REPTILES. 425 2. The ribs, which are also much flattened and exparided, and constitute what are known as the "costal plates" (fig. 164, r). They are generally eight in number on each side, and are commonly united throughout the whole of their lateral margins by sutures. In some cases, however, they leave marginal apertures towards their extremities, and these openings are simply covered by a leathery skin or by horny plates. 3. The margin of the carapace is
. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. DIVISIONS OF REPTILES. 425 2. The ribs, which are also much flattened and exparided, and constitute what are known as the "costal plates" (fig. 164, r). They are generally eight in number on each side, and are commonly united throughout the whole of their lateral margins by sutures. In some cases, however, they leave marginal apertures towards their extremities, and these openings are simply covered by a leathery skin or by horny plates. 3. The margin of the carapace is completed by a series of bony plates, which are called tiie " marginal ; These are variously. Fig. 164.—S eleton of Tortoise (Emjis Enrofced), the plastroji being removed, ca Can pace ; r Ribs, greatly expanded, and united by their edges; s Scapular arch, placed within the carapace, and carrying the fore-limbs ; / Pelvic arch, also placed within the carapace, and carrying the hind-limbs. regarded as being dermal bones belonging to the exoskeleton, or as being endoskeletal, and as representing the ossified cartilages of the ribs (in this last case the marginal plates would correspond with what are known as tire " sternal ribs " of Birds). The " plastron " or ventral shield is composed of a number of bony plates (nine in number), the nature of which is doubt-. 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 Nicholson, Henry Alleyne, 1844-1899. New York : D. Appleton
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