156 Wisconsin Academy of Sciences, Arts and Letters. 



I. Epidermal covering not united with the skeleton, scales or rarely 

 plates; anal opening transverse; teeth present. 



a. Body much elongated, serpentif orm ; limbs wanting; mouth 



dilatable; eyelids none; no urinary bladder Ophidia. 



b. Body elongated; feet usually present; mouth not dilatable; eye- 



lids usually present; urinary bladder present Lacertilla. 



ORDER TESTUDINATA, TURTLES. 



Body more or less perfectly inclosed in a bony or leathery shell-like 

 case, plastron and carapace; epidermal plates usually quadrilateral in out- 

 line; animal variable in form, but generally short, thick-set or flattened; 

 neck generally long allowing of considerable freedom of the head; the head, 

 limbs and sometimes the tail may be completely withdrawn into the area 

 of the shell; the bones of the skull finally became united by complete ossi- 

 fication; tongue thick; jaws forming a horny *beak; food bolted; no teeth. 



KEY TO FAMILIES OF TESTUDINATA. 



I. Plastron very flat and divided into distinct parts which are so hinged, 



by two transverse divisions, as to form, with the carapace, a very 

 perfect box; carapace very convex and deep; animal thickset; toes 

 only slightly webbed; jaws not hooked or but slightly so; food 

 mostly carnivorous Cistudinidce. 



II. Longitudinal section of the shell somewhat ovate in outline, caused by 



the position of the vital organs which are placed far forward, the 

 carapace is thus higher anteriorly than posteriorly; plastron small 

 and cruciform consisting of 12 plates; head and neck very muscular; 

 jaws powerful and more or less strongly hooked; tail muscular with a 

 ridge of horny obtuse or acute processes above, the longest often 

 measuring more than an inch, and with two or more rows of scales 

 underneath; very voracious and extremely fierce; mostly carnivorous 



and aquatic Chelydeidoe. 



in. Longitudinal section of the shell ovate or oval, usually deepest near the 

 center ; edge of carapace obovate or oblong in outline, broadest pos- 

 teriorly; plastron with 12 plates covering the entire imder surface 

 of the body, the anterior lobe sometimes hinged to the posterior; 

 jaws not hooked, obtuse ; carnivorous Emydidoi 



IV. Body placed far back in the shell, causing an obovoid longitudinal 



section; carapace osseous, margins more or less reflexed undei'neath; 

 plastron composed of a variable number of plates, seven, nine or 

 eleven, and hinged, allowing the animal to more or less perfectly close 

 its shell; head pointed; odor strong Cinosternidce. 



V. Shell orbicular or sometimes with an oval or oblong outline ; covered 



by a leathery, more or less flexible skin ; shell never fully ossified, and 



in some species with the ribs projecting; head long and conical Tryonychidce. 



FAMILY CISTUDINIDCE, BOX TURTLES. 



Represented by one genus and two species. Mostly carnivorous, and to 

 some extent decidedly carrion eaters. 



