CHAPTER III. 
Tortoises, Turtles, and Plesiosaurs,— 
Orders Chelonia and Sauropterygia. 
Among all existing reptiles the most easily defined are those commonly known as 
tortoises and turtles, and technically as Chelonians, since the presence of a more or 
less fully developed bony shell investing the body, and containing within it the 
upper portions of the limbs, at once separates them from all other members of the 
class. Indeed, so utterly strange is the conformation of these extraordinary 
UPPER SHELL OF THE CHAIBASSA TERRAPIN, AND A FOSSIL SPECIMEN OF THE SAME IN WHICH THE HORNY 
SHIELDS ARE WANTING. 
reptiles, that if they were met with only in the fossil state they would inevitably 
be regarded as among the most marvellous of all creatures. Here however, as 
elsewhere, the time-honoured proverb holds good, and our very familiarity from 
childhood with the common European land - tortoise undoubtedly tends to 
render us inappreciative of the marvellous bodily conformation of this group 
of reptiles. 
Although the presence of a bony shell is of itself sufficient to distinguish the 
