SOFT-SHELLED TURTLE. 671 
Cistudo ornata, Agassiz. 
Aaassiz, Cont. Nat. Hist. U. S., i, p. 445.—Couzs and Yarrow, Herp. Dakota and 
Montana, p. 266. 
Habitat, Iowa to Upper Missouri. 
Cistudo major, Agassiz. 
Agassiz, Cont. Nat. Hist. U.S., 1, p. 445. 
Florida to Alabama. 
ORDER OPHIDIA. SHERPENTS.* 
Body leng and slender, serpentiform ; limbs none, but rudiments of the pelvic arch 
present in Pythons, Boas, and Tortrices ; epidermal covering above in the form of 
scales, which are periodically cast off and renewed; head often with plates, under sur- 
face usually covered with scutella; integument very extensible ; anal slit transverse ; 
eyelids wanting ; tympanum none; tongue long, bifid, sheathed at base, and capable of 
protrusion ; teeth cenical, not in sockets, situated upon the jaws and palate; mouth 
very dilatable owing to the presence of a quadrats bene ; juga), quadrato-jugal, sternum, 
orbito-and alisphenoids absent; post-frontals, nasals, and lachrymals well developed ; 
rami of lower jaw composed of several pieces ; vertebrae: numerous, the dorsal procelous; 
hear t trilocular, compesed of twe auricles and 2 ventricle, the latter with a partial sep- 
tum; lungs usually one, when two asymetrical; urinary bladder wanting. 
* An erectile poison fang in front part of the mouth; deep pit between the eye and 
nostril. : : 9 4 : 5 CROTALIDA. 
* A permanently erect poison fang in front part of Haine lachrymal pit wanting ; 
extralimital. 6 : 5 : : ELAPIDA. 
* No poison fang in front part of ea: lachrymal pit wanting. . COLUBRIDA. 
FAMILY CROTALIDA. CROTALID SNAKES. 
Teeth in upper jaws few; erectile poison fangs in front; head usually triangular, 
plainly separable from the body; a deep pit between the eye and nostril; dorsal scales 
carinated ; urosteges undivided anteriorly ; species all venomous. 
Tail provided with arattle. a. 
Tail without rattle; cephalic plates large as in Colubride. 0. 
a. “op of head covered with scales, plates if any not reaching further back than 
the eyes. . : : 5 CROTALUS. 
a. Cephalic plates large, ee inate as in Colubride. . . CROTALOPHORUS. 
b. Loral plate present. 6 : . : : : : : ANCISTRODON. 
b. Loral plate absent. : : : . : : ; : TOXICOPHIS. 
GENUS CROTALUS. Linnezus, 
Cephalic region above covered with scales, 2 few large plates may be present anterior to 
a transverse line between the eyes; caudal ratile always present and well developed ; 
body large and strong; pupil of eye vertical; lachrymal or nasal fossa very distinct; 
rosiral plate large, temporals and lajbials small; the two anterior inframaxillaries largo. 
* Wor plates of heads, see U. S. P. R. R. Rep., vol. x; on classification o extralimital 
N,. A. species, see Baird and Girard’s Catalogue. 
