. Zoology : for students and general readers . Zoology. MARSUPIALS. 575 tliey are attached to the nipples at the bottom of the poucli. This hirgo pouch (absent in some opossums and in the Dasyuridce) is supported by two long slender bones attached to the front edge of the pelvis and projecting forward (Fig. 495 m and Pig. 496). In Thylacinus, the Tasmanian wolf, these bones are car- tilaginous. In the opossum, the kangaroo, and probably most marsupials, the young remains in the pouch attached to the nipple, which fills the mouth. " To this it remains at- tached for a considerable period,
. Zoology : for students and general readers . Zoology. MARSUPIALS. 575 tliey are attached to the nipples at the bottom of the poucli. This hirgo pouch (absent in some opossums and in the Dasyuridce) is supported by two long slender bones attached to the front edge of the pelvis and projecting forward (Fig. 495 m and Pig. 496). In Thylacinus, the Tasmanian wolf, these bones are car- tilaginous. In the opossum, the kangaroo, and probably most marsupials, the young remains in the pouch attached to the nipple, which fills the mouth. " To this it remains at- tached for a considerable period, the milk being forced down its throat by the contraction of the cremaster muscle. The danger of suffocation is avoided by the elongated and coni- cal form of the upper extremity of the larynx, which is em- braced by the soft palate, as in the Cetacea, and thus respi- ration goes on freely, while the milk passes, on each side of the laryngeal cone, into the oesophagus" (Huxley). In the car- nivorous forms the brain is low in struc- ture, the olfactory lobes being very large, completely exposed, while the cerebral hemispheres are small and quite smooth. The dentition of marsupials is characteristic, none having three incisor teeth upon each side, above and below, and none but the wombat {Pliascolomys), with an equal num- ber of incisors in each jaw, there being usually more in the upper than in the under jaw. The lowest marsupial is the Tasmanian wolf {Thylacinus), which is rather smaller than the wolf. The Tasmanian devil {Dasyurus ^lrsimls Geoffrey, Fig. 497) is a vicious, trouble- some creature, about the size of a badger. The opossums inhabit North and South America. They have a long tail and a plantigrade step—i. e., they walk on the sole of the whole foot. The Virginian opossum {Didelphys Vtr-. Fig. 497.—Teetli of the Tasmanian devil. The incisors are situated in front of the large conical canine teeth. 2, 3, premolars; m, 1^, four molar teeth.—After Pleas
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
