The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . al plates).With few exceptions this shell is covered with large horny scutesor shields. Super-family I. Cryptodira.—The neck, if retracrile, bends inan S-shaped cur^-e in a vertical plane. The pel\is is not fusedwith the shell, and this is covered with large hornv shields, exceptin Carettochelvs. Family i. Chelydridae.—The plastron is rather narrow, and cross-shaped ; the bridge is ver^^- narrow and is covered by a pair of shields,the displaced abdominals, which are separated from the marginalsby
The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . al plates).With few exceptions this shell is covered with large horny scutesor shields. Super-family I. Cryptodira.—The neck, if retracrile, bends inan S-shaped cur^-e in a vertical plane. The pel\is is not fusedwith the shell, and this is covered with large hornv shields, exceptin Carettochelvs. Family i. Chelydridae.—The plastron is rather narrow, and cross-shaped ; the bridge is ver^^- narrow and is covered by a pair of shields,the displaced abdominals, which are separated from the marginalsby a few mframarginals. The limbs, neck and head are so stoutthat they cannot completely be withdrawn into the shell. Thetail IS very long. Only two genera with three species, confined toAmerica. Chelydra serpentina, the snapping turtle, rangingD ] tlie Canadian lakes through the United States east of theRockies; closely allied is C. rossignoni of Central America andbcuador. Macroclemmys lemmincki, the alligator turtle, isthe largest known fresh-water Chelonian, its shell growing to a length. Fig. 4,—The Snapping Turtle (Chelydra serpentine).of 3 ft. It is characterized by the three series of strong prominentkeels along the back; it inhabits the whole basin of the Mississippiand Missouri rivers. Family 2. Dermatemydidae.—The pectoral shields are widelyseparated from the marginals by inframarginals. the gulars aresmall or absent, and the tail is extremely short. Only a few species,in Central America. The plastron is composed of nine nuchal plate has a pair of rib-like processes like those of theChel>dridae. One or more of the posterior costal plates meet inthe middle line. The shell of these aquatic, broadly web-fingeredtortoises, is very flat and the covering shields are thin. They feed TORTOISE 6q upon leaves, grass and especially fru-it. Staurotypus, salviniwith 23, Dennalemys, e.|. mawi, with 25 marginal shields. Family 3. Cinostemidae.—Closely all
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
