314 POPULAU HISTORY OF THE AQUARIUM. 



renders tliein liable to s^yallow with their aliment a con- 

 siderable quantity of sea-water, there is a beautiful struc- 

 ture lining the interior of the oesophagus, by which this is 

 effectually avoided. This consists of a great number of 

 horny pyramidal bodies with which the whole interior of 

 the oesophagus is furnished, all of them directed backwards 

 towards the stomach ; by which means, althoiigli the food 

 and water together can be readily swallowed, yet when the 

 stomach is retracted, the water can be expelled, and the food 

 itself retained. On Ascension Island, on the shores of the 

 Gulf of Florida, and in many other places, innumerable 

 multitudes of Turtles arrive at a period of year differing in 

 different species, but in all during the early part of summer. 

 It is from the Turtle, and not from the Tortoise properly 

 so called, that the beautifully transparent plates are taken 

 and formed into combs and other articles ; these plates are 

 sometimes eight or ten inches wide. 



Alligators. — (Plate XX.) 



The existence of several young Alligators in the fresh- 

 water basin included within the limits of the Zoological 

 fish-house, living in harmony with Emydida. and Trionij- 

 cJiidce, may seem to give a right to the family of Crocodilida 



