PiF-PTlLES. 2G9 



of the head and tail are alone moveable. The scapular ami 

 clavicular bones are united with both plates, and form an 

 osseous ring for the passage of the trachea and gullet. 

 The legs vary remarkably in form. Some of the species 

 svv'im, others walk, or rather crawl ; and all of them are 

 slow in their motions. 



The testudinal animals are destitute of teeth ; but their 

 jaws, with few exceptions, are provided with a corneous co- 

 vering, like the bill of birds, in some cases, variously notch- 

 ed. The upper jaw is fixed, and the under jaw has a cavi- 

 ty for the reception of the temporal condyle. The tongue 

 is small. The gullet is frequently beset v.ith hard conical 

 processes, having a cardiac direction, and considered as 

 destined to prevent the return of the food. Many of the 

 species are phytivorous, others live on fish. The liver is, 

 in general, divided into two lobes, sometimes a little re- 

 moved from each other. The auricles are large in propor- 

 tion, with thin walls ; and, at their opening into the ventri- 

 cle, are furnished with valves. Walls of the ventricle co- 

 vered with fleshy eminences. The lungs are double, and 

 nearly of equal size. The windpipe divides near the larynx; 

 and, in some species, each branch makes a turn before reach- 

 ing the lungs. 



The kidneys are rather diminutive in size. The blad- 

 der of urine, however, is of extraordinary dimensions. The 

 urine itself is transparent and watery, and, besides a little 

 mucous and common salt, contains uric acid *. 



In the reproductive system, the sexes are observed to be 

 on separate individuals. The external male organ is cylin- 

 drical and pointed, with a groove along its whole length. 

 The oviducts have each an enlargement, or uterus. The eggs, 

 which are fecundated internally, resemble those of birds, in 

 being covered with a calcareous shell. These are depositeil 

 by the females in the sand, and left to be hatched by tiu^ 



• Dr J. Davy. Phil. TranF. 1818, p. ?06. 



