108 
NATURAL HISTORY. 
[N. ZOOL. GAL, 
by sailors, who procure them from the Gallapagos, where they have 
been lately introduced, and have increased very rapidly. 
In most of the genera, as Testudo , Homopus , and Chersina , the 
thorax and sternum are solid. The tw o former have twelve sternal 
shields. Testudo has five toes on the fore and four on the hinder 
feet; the Homopi have four toes on each foot. The Chersince have the 
same number of toes as the Testudines, but have only a single shield in 
the front of the sternum. The Kinixys have the hinder part of the 
thorax moveable, and the inguinal plates very large, and the Pyxes are 
like round tortoises, but the front part of the sternum is moveable like 
the lid of a box. The caudal plates of the recently hatched specimens 
are divided. 
The Tortoises which live in fresh water have a more depressed shell; 
their feet are expanded and webbed between the toes, and the latter are 
furnished with sharp claws. They are divided into three families. 
The first of which, the Terrapins, (Emyd^e, Cases 21, 22) have eleven 
or twelve horny plates on the breast-bone or sternum, and withdraw 
their head and neck between the shells; their pelvis is only attached to the 
vertebra. Most of the genera have a moderately sized head and tail, 
and the suture between the thorax and sternum simple; some of them 
have a solid sternum truncated in front and niched behind, and the 
sternum, wdiich has twelve plates, is united to the thorax by a bony 
suture, as the genera Geoemyda , which have short toes; Emys, wdiich 
have elongated longly clawed toes. Tetraonyx differs from the latter 
in only having four toes on the fore feet, and Cyclemys in having some 
small scales on the sterno-costal suture, and Malachemys differs from all 
the preceding in having its head covered with a soft skin like the neck. 
The Box Terrapins, or Cistudce, have the sternum, which is rounded 
at each end, divided by a central cross suture, and only attached to 
the thorax by a ligamentous suture. The Kinosternons have the 
sternum, which has only eleven plates, divided by tw r o cross sutures, and 
its central part attached to the thorax by a bony symphasi^. In the 
other genera the head is larger, and the suture betw een the thorax and 
sternum is covered by some peculiar plates, as the Crocodile Tortoise 
( Chelydra), which has a large crested tail and a cross-like sternum, 
acute before, covered with ten sternal plates, and with a broad one on 
each side ; and Platysternon , w hich has a broad fiat sternum truncated 
in front, covered with twelve plates ; the sterno-costal suture covered 
with three additional plates, and the tail elongate, cylindrical, shielded. 
These tortoises are much used as food by the Americans and the natives 
of India. Amongst these is a monstrosity with two heads. 
The second family ( Chelydje, Case 22) have an additional horny 
plate on the front of the sternum, and they bend the neck back under the 
side margin of the shell; their pelvis is attached to the back-bone and 
the hinder part of the thorax. In most of the genera the jaws are horny 
like the other Tortoises. In Sternotherus, the front lobe of the sternum 
is moveable and separated from the rest by a cross suture. In the 
other genera it is solid, and the lobes are broad. The Chelodinoe and 
Hydromoedusoe have four toes on each foot; the former has the head 
covered w T ith a hard skin and the intergular plate within the margin, and 
the latter has the skin of the head soft, and the intergular plates, like 
the rest of the genera, on the edge of the sternum. The Pelomedusce 
