LAND - TOR TORSES , 
47 
The Land-Tortoises and Terrapins. 
Family TESTUDINID.E. 
The land-tortoises, together with the greater number of the fresh-water 
tortoises, or terrapins, of the Northern Hemisphere, as well as their southern 
allies, collectively constitute one of several families belonging to the first great 
group of the order. From the circumstance that all its 
members are so constructed as to be able to withdraw 
their heads within the margins of the shell by a bending 
of the neck in an S-like manner in a vertical plane, the 
group may be conveniently designated S-necked tortoises; 
their scientific designation being Cry'ptodira. Since, how¬ 
ever, the soft-tortoises likewise retract their heads in a 
similar manner, it is obvious that this character alone will 
not suffice to define the group, and it must accordingly be 
supplemented by others. Although the degree of ossifi¬ 
cation of the shell is very variable in the group, the 
carapace and plastron being in some cases welded into a 
complete box, and in other instances separate, yet there 
is invariably a complete series of marginal bones, con¬ 
nected with the ribs; the presence of the full series of 
marginals, together with the S-like retraction of the neck, 
being sufficient to distinguish the group. A peculiarity 
in which the members of the group differ from those of 
the next one, is to be found in the circumstance that the 
bones of the pelvis remain throughout life unconnected 
with the plastron; while in the greater number of cases THE LEFT HALF 0F THE PLAS ' 
. , , . . • n • n • TRON OP THE CHAIBASSA 
the latter, as shown m the accompanying figure, comprises terrapin. 
only six pairs of horny shields, their being no intergular 
shield between the first pair, or gulars. The skull is characterised by the tympanic 
ring (t in the accompanying figure) having a notch in its hinder border, and also 
by the condyle on its quadrate - bone 
fitting into a hollow at the hinder end 
of the lower jaw. This S-necked group 
includes the marine turtles, and all the 
tortoises of the Northern Hemisphere, 
with the exception of the soft river- 
tortoises, and thus comprises by far the 
greater number of the living represent¬ 
atives of the entire order. Although well 
represented in Africa and South America, 
the group is quite unknown in Australia. 
The land-tortoises and terrapins of the family Testudinidce have the shell 
well developed and of a more or less ovoid shape; the plastron being connected 
with the carapace either by a straight articulation or by means of sutures, while 
SIDE VIEW OF THE SKULL OF A LAND-TORTOISE, WITH 
THE LOWER JAW REMOVED. 
