166 



SUBKINGDOM VBETEBBATA. 



consolidated into an upper shell called the Carapace, while 

 the broadened sternum forms a lower one termed the Plas- 

 tron.* Into this portable cas- 

 tle the reptile retreats with 

 marvelous rapidity, f in one 

 genus the limbs and head be- 

 ing withdrawn so as to show 

 no apparent opening. The 

 viscera, the shoulder and hip- 

 bones, and the muscles are all 

 packed in the thorax. Breath- 

 ing is performed by enlarging 

 the cavity of the mouth, when 

 the air rushes in through the 

 nostrils, and by contraction is forced down the windpipe. 



SMetan of a Marine Turtle. 



Q S 

 3 u- 



TRUNCATED AND UNIT- 

 ED TO TUB NAILS. 



Testiidinidas, Cishldo virgjniana, Box Tortoise. 



FLATTEN- 

 ED. WITH 

 DISTINCT 

 TOES. 



f Emydn 

 ( Clielyd 



SCALES, ) 



Caraface 



COVERED 

 WITH 



idiE, 



lelydidBB, 



Chelydra serpentina, Eiipr Torloifie. 

 Chelys matamata, Bearded Tortoise. 



CARAPACE 



COVERED BY 



A FLEXIBLE 



SKI.V. 



. TrionychidfB, TrionyTt ferox, 



FLATTENED AND 



FORMED INTO PADDLES 



FOR SWrMMIN(i, WITH 



TOES CONCEALED. 



Snapping Tortoise. 



Chelonidffi, Chelonia midas, Green Turtle. 



Testudinidffi.— The Land Tortoises J have feet formed 

 only for walking, and hence they never enter the water. 

 Their food consists of soft plants, as mushrooms. The plas- 

 tron of the female is convex, and that of the male concave. § 



* Tlie same number of pieces is found in the skeleton as in the ordinary i erte- 

 hrates, the shape and t^ize alone being changed. 



t The long, slender muscles which move the flexible neck are tied to the under 

 side of the carapace. When dried they may be capable of producing musical sounds 

 and thus have given rise to the poetical legend of the origin of the lyre. 



t Many authors use the terms tortoise and turtle synonymously ; but the former 

 term is properly applied to the land species, and the latter to the marine. 



§ The " Oopher," a small tortoise abont eighteen inches long, found at the South, 

 belongs to this family. It will burrow six feet in the ground. 



