88 



TORTOISES AND TURTLES. 



This turtle is generally distributed throughout the tropical portions of the 

 Atlantic, Indian, and Pacific Oceans, from whence it occasionally wanders to the 

 coasts of cooler regions. Yearly becoming scarcer, it is, however, one of those 

 species which stand a fair chance of extermination at no very distant date. 

 Although but little is known as to the mode of life of this turtle, it appears that 

 its food is chiefly of an animal nature, comprising fish, crustaceans, and molluscs. 

 In the breeding-season it appears in numbers on the Tortugas Islands, off the coast 



of Florida, and sometimes in still greater abundance on 

 the sandy shores of Brazil. Arriving somewhat later than 

 the true turtles, it deposits its eggs in a similar manner, 

 laying as many as three hundred and fifty, in two batches ; 

 while at times, when three or more females have a nast in 

 common, upwards of a thousand eggs may be found in 

 a single spot. When hatched, the young turtles immedi- 

 ately seek the water, where, however, they have almost 

 as many foes as on land ; so that it is probable only a 

 very small percentage arrive at maturity. The strength 

 and weight of a full-grown individual are very great ; one 

 captured some years ago, on the coast of Tenasserim, 

 requiring the combined efforts of ten or twelve men to 

 drag it on to the beach. The flesh has an unpleasant 

 flavour, and is not, therefore, generally eaten. 



Gigantic as is the existing leathery turtle, it was 

 considerably exceeded by some of its extinct allies. 

 Among these, the huge Eosphargis, from the London Clay, 

 with a skull of nearly a foot in length, apparently had a 

 carapace consisting only of one median row of broad-keeled bony plates, and a 

 border of marginal bones; while in Psephoph&rus, from the higher Eocene and 

 Miocene strata of the Continent, both upper and lower shells were formed of 

 mosaic-like bones, which, it is thought, were overlain by horny shields. In the 

 earlier Protostega and Protosphargis, from the Cretaceous rocks of North America 

 and Europe, the upper shell appears to have been represented merely by a row of 

 marginal bones, while the lower one was very stoutly ossified ; some of these early 

 forms probably attained a length of from 10 to 12 feet. 



FRONT VIEW OF LEFT HUMERUS 

 OF AN EXTINCT LEATHERY 

 TURTLE. 



The Side-Necked Tortoises. 

 Families CHELYID^E and PELOMEDUSIDM. 



In place of withdrawing the head into the shell by means of an S-like 

 flexure of the neck in a vertical plane, as in all the groups hitherto described, 

 the remainder of the living tortoises with complete shells bend the neck side- 

 ways in a horizontal plane (as shown in the illustration on p. 92), and thus 

 bring the head within the margins of the shell. Accordingly, the group is 

 collectively spoken of as the side-necked tortoises, or Pleurodira. This character 

 is alone amply sufficient to separate the group from the foregoing assemblage 



