AMPHIBIANS AND REPTILES. 257 



AMPHIBIANS AND REPTILES. 



' BY ALEXANDER G. RUTHVEN. 

 GEOGRAPHIC RELATIONS OF THE FAUNA. 



The writer gave particular attention to the amphibians and reptiles 

 on this expedition, and in this work he was assisted very materially 

 l)y the other members of the party. To one interested in the herpet- 

 ology of Michigan the results obtained in this summers work are very 

 gratifying; for while our Michigan fauna is composed of species which 

 are of wider range in eastern North America, and thus for the most 

 part well known, comparatively little is know^n of the distribution of 

 many of these forms in the state. This is particularly true of the north 

 and south distribution, an interesting question in view of the inter- 

 mediate position of the state between northern and southern faunas. 

 The remarks on the general nature of the fauna of Michigan in an 

 earlier paper in this report apply equally to this group, and we find 

 as we go northward that the species that inhabit the extreme southern 

 tier of counties gradually drop out of the fauna until few are left on 

 our northern boundary. In the case of amphibians and reptiles, how- 

 ever, we do not, as in the case of mammals and birds, have many other 

 forms coming into the fauna from the northward, and the explanation 

 is that these groups are preeminently tropical and are in this region 

 reaching the outskirts of their range. This is less true of the am- 

 phibians than of the reptiles, for the former have a greater capacity for 

 enduring cold. It is thus not surprising that the only two forms that 

 enter our region from the north belong to the genus Rana (the frogs). 

 These species are Rana cantahrigensis and R. septentrionalis, both of 

 which are of decidedly northern distribution, the latter not occm-ring 

 in the southern peninsula, so far as we know, and both ranging tlirough 

 the northern peninsula and far into Canada. 



From these general remarks, it will be seen that the rei)tile-amphibian 

 fauna of the region studied may be divided into three groups: 



1. Those forms that are known to occur throughout the state, or 

 at least range well north of this latitude. The species that fall into 

 this group need no discussion here. They include most of the am- 

 phibians and may be enumerated as follows: Bufo americaii'us, Rana 

 pipiens, R. clamitans, Ilyla pickeringi, H. versicolor, R. sylvatica can- 

 tahrigensis, Ambystoma jefjersonianum, Diemictylus viridescens, Plct- 

 33 



