FAMILY CHELONID^. 23 



Description. Shell oblong, narrow in front, broader and more erected behind ; the dorsal 

 outline descends rather more abruptly behind ; slightly carinated on the dorsal ridge. The 

 first vertebral plate triangular, with its truncated axis behind ; the three following hexagonal, 

 the last smaller than the two preceding ; the posterior plate sub-pentagonal, the posterior plates 

 distinctly imbricated. Lateral plates large, the anterior irregularly subquadrate ; the two 

 following higher than broad, pentagonal ; the last smallest, and also pentagonal ; the interme- 

 diate marginal plate smallest, sub-quadrate ; the remainder oblong, the four posterior largest ; 

 all, except the last two, separated from the shell by a groove. Sternum small, narrow, widely 

 emarginate behind, composed of eleven plates, all with concentric angular striee, and minute 

 radiating stris ; the anterior intermediate or united ; gular very small, triangular ; brachial 

 small ; abdominal plates largest, and apparently immovable. Head and neck capable of pro- 

 trusion an inch and a half from the shell. Head very large, pyramidal, four-sided, pointed, 

 and slightly truncate in front. Eyes moderate. Nostrils large, contiguous, and placed at the 

 extremity of the snout. Two short yellow fleshy tentacula imder the chin, and two rather 

 larger behind. Skin of the tliroat and neck granulate. All the feet with acute incurved 

 claws, distinctly webbed ; the place of the fifth claw on the posterior foot supplied by a broad 

 web. The outer and inner margins of the feet furnished with a cuticular membrane, elevated 

 into points. Scaly plates on the anterior surface of the fore feet, and on the under side of the 

 hind feet. Tail very robust at the root, with several series of pointed processes, often with a 

 horny tip. 



Color. The color and markings of this species not easily detected in the recently caught 

 animal, as it is usually covered with an agglutination of mud and aquatic plants ; when 

 cleansed, the shell appears of an olive brown or green, obscure, radiating dark stripes on the 

 lateral plates, and similar longitudinal ones on the marginal plates. Sternum reddish brown 

 or flesh-color, with a few indistinct dark blotches. Pupils black ; iris golden. Head black 

 or deep olive green. A yellow line on each side passes from the nostrils over the eye upon 

 the neck ; another somewhat broader, from beneath the nostrils, and meeting in front, passes 

 backward under the eye upon the neck ; a third, shorter, proceeds from near the symphysis 

 of the chin, extending on each side of the lower jaw. Feet and tail reddish brown. 



Length, 2'5. 



Ditto of tail, 0-8. 



Height, 1-2. 



These dimensions are from a small specimen ; the ordinary size is tluree inches : it is the 

 smallest of our tortoises yet discovered. This species is one upon which modern systematists 

 have expended much labor, the result of which may be seen in the list of synonimes. 



The Musk Tortoise or Mud Turtle, Mud Terrapin or Stink-pot, (with other equally savory 

 popular names,) is to be found in most of our ponds and ditches. It occurs from Maine to 

 Florida, but its western limits are unknown. We know from Kirtland, that it occurs in the 

 northern waters of Ohio. It appears to be an active, vigorous animal, biting with considera- 

 ble vigor when irritated. There appears to be two varieties, of which one is smooth on the 

 shell, while the other is sub-carinate. 



