192 AFFINITIES AND GEOGRAPHICAL 



FIG. 101. 



Emysaura Serpenlina. 



Last are the land Tortoises (Testudines], in which, with a 

 perfect osseous case, there are extremities formed entirely for 

 land progression, terminating in rounded callous stumps, with 

 indistinct unguiculate toes. These animals are found in tro- 

 pical regions all over the earth. Generally they are of small 

 size ; but in the Galapagos Islands Mr. Darwin found them 

 several feet in length, and we know that in the tertiary era 

 there were species in India of colossal proportions. The 

 greater number of the land tortoises are vegetable feeders, and 

 similar in disposition to the herbivorous turtles. A small group 

 of species, already adverted to, stand apart, as exhibiting im- 

 mediate affinities to the emydes. 



Seeing the various characters of the Chelonia, and keeping 

 in view the principles of the genealogical system, we have good 

 reason for believing that two or more stirpes exist in this order 

 of animals. The herbivorous species of sea arid land un- 

 doubtedly form portions of one family, the transition from the 

 one to the other being attended by little besides a slight con- 

 version of the extremities, a maturing of the development of 

 the osseous case, and that reduction of bulk which is every- 

 where seen in terrestrial advances from marine originals. 

 Another stirps, perhaps starting in the coriaceous turtle, involves 

 the Tryonices, or Soft Tortoises, which may be regarded as 

 having merely passed from a marine to a fluviatile life, as has 

 been done in many other instances. The Emydes, for which 

 an original may be found in some of the other carnivorous 

 turtles, constitute another line terminating in certain land 

 species. On the Chelydes it would perhaps be premature to 

 speculate. In our investigations in this order, it is highly in- 

 structive to mark the improvement in the filling up of the 



