7 8 
TORTOISES AND TURTLES. 
Maw’s Terrapin. 
brown or blackish, while the head and neck are brown with yellowish spots. 
From other species of the genus it is distinguished by the large size of the plastron, 
in which the anterior lobe is narrower than the mouth of the shell. 
In general habits the mud-terrapins seem to be very similar to the fresh-water 
members of the tortoise family, although they prefer swamps and marshes to 
running waters. Carnivorous in their diet, they subsist chiefly on small fishes, 
insects, and worms, while they have been observed to capture newts. They will 
readily take a baited hook, and when thus caught sink rapidly and heavily to the 
bottom, thus causing the angler to believe that he has hooked a weighty fish. At 
the commencement of winter they bury themselves in moss, where they remain 
dormant till the following May. An extinct genus nearly allied to the mud- 
tortoises occurs in the Tertiary rocks of Baden. 
Maw’s terrapin ( Dermatemys mawi) may be taken as a good 
representative of the second family, all the three genera of which are 
restricted to Central America. This family connects the preceding one with the 
snappers, agreeing with the latter in the presence of an entoplastral bone, and with 
the former in the characters of the vertebrae of the short tail, which have the cup in 
front, and the absence of a roof to the temporal fossa of the skull. Maw’s terrapin 
and its allies further agree with the mud-terrapins in the incompleteness of the 
series of neural bones of the carapace; the hinder ones being wanting, and thus 
allowing the costal plates to meet in the middle line. Externally, the members of 
the present family may be distinguished from the Testudinidce by the presence 
of an additional series of infra-marginal shields between the marginals and those 
of the plastron—a feature which they possess in common with the big-headed 
tortoise and the snappers. Maw’s terrapin, which attains a length of some 
15 inches, and is the sole representative of its genus, has the plastron large, and 
connected with the carapace by an elongated bridge; the gular shield being single, 
and the usual five other pairs of shields being present on the plastron. Unlike 
most other tortoises, there are twelve pairs of marginal shields, in place of the 
usual eleven. In the other two genera of the family— Staurotypus and Claudius 
—the plastron is reduced to a cross-like shape, and has but a short connection with 
the carapace; while the number of paired shields on the former is only four or 
or three, and the chin is provided with a pair of wattle-like appendages, of which 
there is no trace in Maw’s terrapin. While in the two species of Staurotypus the 
plastron is connected with the carapace by a bony bridge, in the single represen¬ 
tative of Claudius the junction is entirely ligamentous. This family is represented 
by several extinct genera in the Tertiary and Cretaceous strata of North America, 
one of which ( Baptemys ) had the full series of neural bones; and there appear 
to have been allied forms in the European Tertiaries. 
The Snappers and Alligator-Terrapins. 
Family CnEL YDRIDsE. 
Resembling the big-headed tortoise in the great relative size of their hook- 
beaked heads, and their elongated scaly tails, the snappers and alligator-terrapins 
