MUSK TORTOISE. 667 



ginals much the higher, making an upward curve or indentation into the posterior cos- 

 tal on each side ; last Tertebral qaadrangular, broadest behind, with a slight projection 

 downward between the two posterior marginals ; first neural elongated, broadest 

 anteriorly ; vertebrals slightly imbricated, alternating with the oostals ; carapax slightly 

 emarginate behind, arched upward over the neck; gular plate nearly triangular, the 

 remaining sternal shields more or less quadrilateral ; abdominal much the largest ; tail 

 short, with several rows of pointed warts ; neck, legs, and feet granulated ; fore legs 

 with scaly plates, and bases of feet with scales ; no plates on the posterior limbs. 

 Length of carapax, 4^ inches ; height of carapax. If inches ; breadth of carapax, 3 inches ; 

 length of tail, 1 inch. 



' Habitat, Maine, Maasaohusetts, New York, South Carolina, Georgia, Florida, Alabama, 

 and Louisiana, to Tennessee, Ohio, Michigan, Indiana, and Missouri. 



The Musk Tortoise inhabits ditches and ponds, burying itself in mud. 

 It is an active animal, .and bites with considerable vigor if irritated. It 

 has a very disgusting odor from which, with its habits, it has received 

 not only its specific, but also its various common names, such as Musk 

 Turtle and Stinkpot in the north, and Mvd Terrapin in the south. It 

 occurs in Northern Ohio and probably also occasionally through the 

 whole State. It oviposits in June and July. 



FAMILY TRIONYCHID.^. THE SOFT-SHELLED 



TURTLES. 



Carapax in the form of a flattened orbicular disk, never completely ossified, its mar- 

 gins soft and flexible, and in some species with the ribs projecting; costal plates when 

 visible eight pairs ; posterior margin of carapax extending much beyond the body ; 

 sternum composed of four pairs of bones and one odd one ; plastron a leathery covering 

 with or without the sternal bones being visible externally ; feet broadly palmate ; head 

 and neck very long and flexible ; nostrils carried forwards by a long tubalar projection ; 

 temporal arch narrow ; parietal bones slightly if at all projecting outward ; pterygoids 

 broad, with slight depressions on their external edges ; sphenoids extending forward 

 between the pterygoids to the palatines ; inner nares large, and situated far back. 



The TrionychidcB are usually found at the bottom of shallow water buried in mud. 

 They remain thus buried, raising their head and long flexible snout to the surface for 

 the purpose of respiration. Thus the long flexible aeck, head, and snout as well as the 

 soft covering correspond to the habits of the animal, aa a hard carapax and plastron 

 aie unneoesaary for the purposes of protection to them while buried in the mud. In 

 burrowing they go under a thin layer horizontally by digging with the fore feet, brac- 

 ing and pushing the bedy under with the hind ones. 



• Septum of nose without any internal ridges on each side. . . . Amtda. 



* Septum of nose with a ridge ou each side Aspidonkctes. 



Gbnus AMTDA. Schweigger. 



Headlong, narrow, and pointed anteriorly; horizontal alveolar surface of jaw nar- 

 row, broadest behind, and with a downward curve of the upper under the eye ; lower 



