TORTOISES AND TERRAPINS. 



51 



and brown in the females. Box-Tortoises are kept as pets in 

 the United States, and attain a great age. 



The Pond-Tortoises {Emys, 109, 110) are the typical and least Case 6. 

 specialised members of a large, number of, for the most part aquatic, 

 genera, which diverge in one direction into the thoroughly aquatic 

 Batagurs and in the other into the land Tortoises. They have more 

 or less depressed shells and generally webbed feet ; and the majority 

 are carnivorous. The distinctions between the different genera are 



Fig. 52. 



The Painted Terrapin (Chrysemys pida) ; J nat. size. (No. 36-) 



chiefly based on the form and relations of the bones of the shell, the 

 structure of the skull, etc., so that they are not apparent externally. 

 The Pond-Tortoises, gf which there is one European and one 

 North American species, are thoroughly aquatic, and feed on small 

 fishes, W'orms, etc. ; during winter they bury themselves in the mud. 

 Nearly allied is Clemniys {\ \ \-\ 15), one European species (C. leprosa^ 

 1 15) of which is characterised by its offensive smell and the growth of 

 a fungus on the shell. The well-known salt-water Edible Terrapin 

 {MaJacodemmys terrapin, 91), of the United States, belongs to a 

 kindred genus distinguished by the breadth of the palatal surface of 



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