. Elements of comparative zoology. Zoology. MAMMALS. 365 absence of a pelvis in these forms allows no line to be drawn between lumbar, sacral, and caudal regions. In the skull there is a tendency for bones which are distinct in the fishes and reptiles to fuse with each other, so that the number of distinct elements is considerably reduced. The skull is borne on the first cervical vertebra (atlas) upon which it slides by means of two rounded sur- faces or condyles. The lower jaw articulates directly with the skull, and is never suspended by a quadrate bone, as in all other classes of vertebrate
. Elements of comparative zoology. Zoology. MAMMALS. 365 absence of a pelvis in these forms allows no line to be drawn between lumbar, sacral, and caudal regions. In the skull there is a tendency for bones which are distinct in the fishes and reptiles to fuse with each other, so that the number of distinct elements is considerably reduced. The skull is borne on the first cervical vertebra (atlas) upon which it slides by means of two rounded sur- faces or condyles. The lower jaw articulates directly with the skull, and is never suspended by a quadrate bone, as in all other classes of vertebrates, the cyclostomes FIQ. 157.—Brain of dog. (After Wiedersheim.) II-XII, the cranial nerves (see page 299). The fore limbs are always present; the hind limbs are absent in the whales and manatees, being represented in a few forms by one or two bones imbedded in the muscles of the trunk. Except in the Monotremes (p. 369), the cora- coid does not occur as a distinct bone, but as a small prominence joined to the shoulder-blude (scapula), while in many the collar-bone (clavicle} also is lacking. The feet have typically five toes, but not infrequently this number is reduced by a disappearance of the outer digits, the reduction reaching its extreme in the cow, which has but two, and the horse, which walks upon the tip of its middle 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 Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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