THE MUD TERRAPINS AND THEIR ALLIES 2435 



genus is the Pennsylvania!! mud terrapin (C. pennsylvanicum} , which attains a 

 length of about four and one-half inches, and inhabits Eastern North America from 

 New York to the Gulf of Mexico. In color, the shell is brown or brownish above, 

 and either yellow or brown beneath, the lines of junction between all the shields 

 being dark brown or black, 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 run- 

 ning 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 com- 

 mencement 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 mawt) may be taken as a good repre- 

 sentattve 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 characteristics 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 

 Testudinidcz by the presence of an additional series of infra-marginal shields be- 

 tween 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 fifteen 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 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 spe- 

 cies of Staurotypus the plastron is connected with the carapace by a bony bridge, in 

 the single representative of Clatidius 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. 



