MUSK TORTOISE. 667 
ginals much the higher, making an upward curve or indentation into the posterior cos- 
tal on each side; last vertebral quadrangular, broadest behind, with a slight projection 
downward between the two posterior marginals; first neural elongated, broadest 
anteriorly ; vertebrals slightly imbricated, alternating with the costals ; 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, 44 inches ; height of carapax, 1$inches; breadth of carapax, 3 inches; 
length of tail, 1 inch. 
Habitat, Maine, Massachusetts, 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 
Turile and Stinkpot in the north, and Mud Terrapin in the south. It 
occurs in Northern Ohio and probably also occasionally through the 
whole State. It oviposits in June and July. 
feamanyY TRIONYCHEVAS (THE SOPT-SHELIED 
TURTLES. 
Carapax in the form of a flattened orbicular disk, never completely ossified, its mar- 
gins soft and flexible, and in some species with tho 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 tubular 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 Trionychid@ 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 neck, head, and snout as well as the 
soft covering correspond to the habits of the animal, as a hard carapax and plastron 
aie unnecessary 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... : : AMYDA, 
* Septum of nose with a ridge on each side. . z . : . ASPIDONECTES, 
Genus AMYDA. Schweigger. 
Head long, narrow, and pointed anteriorly; horizontal alveolar surface of jaw nar- 
row, broadest behind, and wiih a downward curve of the upper under the eye; lower 
