Identifier: introductiontozo00dave Title: Introduction to zoology; a guide to the study of animals, for the use of secondary schools; Year: 1900 (1900s) Authors: Davenport, Charles Benedict, 1866-1944 Davenport, Gertrude Anna Crotty, 1866- Subjects: Zoology Publisher: New York, Macmillan company London, Macmillian and co., ltd. Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

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Text Appearing Before Image: ted with the habit of gnawing. This groupis very abundantly represented in North America, moreso, indeed, than in other continents. All our rodents fallinto seven families: (1) the squirrels, gophers (Fig. 295),prairie dogs, and wood chuck, with long and hairy tail ;(2 ) the beaver, with broad and scaly tail ; (3) the pouchedgophers, with peculiar cheek pouches opening outside the 1 From roder f, to gnaw. THE MOUSE AND ITS ALLIES 321 mouth; (4) the jumping mice, with greatly elongatedhind legs; (5) the muskrat and the various wood andfield mice, closely related to the genus Mus ; (6) the por-cupines, with bristles replacing hairs; (7) the hares, withlong ears and short tails. All of these familiar rodentsare, on the whole, destructive to agriculture. As thereare, however, other interests in life than agriculture, it is tobe hoped that the warfare against our native rodents willnot be too relentlessly pursued. At least one interest-ing species has been rendered well-nigh extinct by the

Text Appearing After Image: FIG. 296. — Ortiithorhynctius atiattnus, the duckbill. After Vogt and Specht. avarice of fur hunters - - this is the American beaver, ananimal which has developed extraordinary instincts for theconstruction of dams and subaquatic passages. Other Mammals.- The Monotremata1 are the lowestmammals, and in many ways seem to connect the classwith reptiles or amphibians. The milk glands are in a s, single, Tprjua, hole or opening ; so called because urinary, geni-tal, and alimentary canals have a common external opening. 822 ZOOLOGY low state of development and eggs are laid, as in reptilesand birds. There are two principal types, - - the Duck-bill (fig. 296), with aquatic habits, and the SpinyAnt-eaters (Echidna, Fig. 297), inhabiting rocky places.Both types are confined to Australia and neighboringislands. The Marsupialia ! have a remarkable distribution overthe earth to-day. All are confined to Australia and adja-

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