76 HERPETOLOGY OF MICHIGAN. 



turtles. Only in the case of the latter should the string be tied so 

 tightly as to crease the skin. 



DESCRIPTIONS OF MICHIGAN REPTILES. 



CLASS REPTILIA. 



The living reptiles are cold-blooded vertebrates that breathe by 

 means of lungs and usually have a covering of horny epidermal 

 scales; the latter sometimes supported by bony dermal plates. The 

 only Michigan species that does not have the body covered with 

 scales is the soft-shelled turtle {Platypeltis spinifera). In external 

 form the body is elongate and limbless (snakes), somewhat elongate 

 and usually quadrupedal but occasionally apodal (lizards and croco- 

 dilians), cuirassed and quadrupedal (turtles). The quadrupedal 

 lizards are frequently confused w^ith salamanders, but the quadiTi- 

 pedal salamanders (which alone occur in Michigan) always lack 

 the bony or horny covering characteristic of reptiles, the skin being 

 thin and moist. The apodal lizards are frequently confused with 

 snakes, but the only apodal lizard in northeastern North America, 

 the so-called glass snake {Opliiosaurus ventralis), may always be 

 distinguished from snakes by the presence of eyelids and external 

 ears. This lizard has never been recorded from Michigan, although 

 it is said to occur in Wisconsin. Numerous morphological char- 

 acters other than those given characterize the Class Reptilia and 

 may be found by referring to any vertebrate zoology. 



Dlstrihution of the Class Reptilia in Michigan. — The distribution 

 of each species is discussed in detail with its description. In gen- 

 eral the reptile fauna of the state is characterized by the small 

 number of forms. This is due in large part to the northern latitude 

 of the region, as the reptiles are primarily a tropical group. The 

 influence of temperature upon the distribution is also shown within 

 the state. It is true in both orders that as one goes northward 

 from the southern boundary of the state the number of species 

 gradually decreases. Thus it may be seen by an examination of 

 the maps that twenty-five or all but one of the species in our fauna 

 have been recorded from the two southernmost tiers of counties 

 while only six have thus far been found in the northern peninsula, 

 and only one occurs there and not in the southern peninsula. It 

 must be admitted, of course, that our information on the intrastate 

 distribution of the species is far from complete, but enough has 

 been learned to make it quite evident that further work will not 

 overthrow this conclusion. 



