INTRODUCTION. 
Ill 
of no small satisfaction ; whilst the results, in the elucidation of the geographical 
distribution of animals, and still more in ascertaining the identity or diversity 
of recent and fossil species, give to this more humble branch of our zoological 
studies, an importance which does not at first sight appertain to it. 
To all these objects the writer of Monographs essentially contributes. He 
acts as the pioneer, removing obstacles, and clearing the ground to be after¬ 
wards occupied by the more efficient force, whose evolutions would be con¬ 
tinually impeded and their plans disordered, but for the assistance of their 
laborious predecessors. 
In composing a Monograph of the present Order, there is no difficulty in ascer¬ 
taining its exact limits, nor danger of committing the error either of introducing 
an individual belonging to any approximating group, or of rejecting as doubtful 
any one which really appertains to this. There is in fact scarcely any group 
of animals which, according to our present knowledge, is so distinctly circum¬ 
scribed by peculiarity of structure, as the Testudinata. The circumstance of 
the limbs being placed within instead of on the outside of the trunk, and the 
osseous union of the ribs, forming a sort of bony box, including not only the 
viscera but the members, are characters which at once separate them from every 
other known group. Whether future investigations, either in recent or espe¬ 
cially in fossil zoology, may discover the links by which these singular animals 
are connected, by continuous affinity, with any of the groups from which at 
present they appear to be so distinctly separated, we cannot now even con¬ 
jecture ; but at present they certainly remain the most isolated order, not only 
amongst the Reptilia, but perhaps in the whole animal kingdom. 
As the species which inhabit the Continent of Europe and the seas which 
were navigated by its ancient inhabitants, are but few, we look in vain to the 
Classical writers on natural subjects for any but the most vague and uncertain 
notices respecting them. That the four species of marine turtles were known 
both to the Greeks and Romans, is indeed scarcely to be doubted, as three of 
them are occasionally found in the Mediterranean, and the fourth, Chelonia 
imbricata, furnished their merchants with the precious tortoise-shell,—an article 
of luxurious decoration, which appears to have been much used in ornament- 
mg the palaces and villas of the Roman nobles. The soft-bodiecl species of this 
