Mexican Amphibians and Reptiles. 709 
Of the former 4 are restrieted to above 7000‘ and 2 more are centred 
at that level, and only one extends down to 2000 feet, whilst none 
are found at sealevel. But of the 14 long-ranged species one only 
is restrieted to above 7000‘ and one only is centred up that level, 
whilst two are centred just within the Hotlands, and 8 in all reach 
the sealevel. 
These Nearctics are further remarkable for the few species 
which are confined to a strietly temperate range. Most of them 
being rather long-ranged, naturally extend either into the cold or 
into the hot zones. The mean of the whole number of specific centres 
works out at 5700‘ feet and this agrees well with the mean average 
altitude which can be deduced from the diagrammatie list of the 
Nearcties. Most of their short-ranged species belong to the cool or 
cold zone. That there are so many long-ranged Nearctics, is only 
another expression of the fact that these Nearctics are more 
accommodating than plastie. Those which are plastic, 
have mostly modified for cold life. If we consider the 24 
Nearctics and naturalised Mexicans with their average best suitable 
level of between 5000 and 6000 feet, one third have found their 
way down to sealevel, although none of these have qualified for ex- 
clusively Hotland life; one fourth are modified entirely for the cold 
zone. Consequently the Nearctics are more influenced 
N De BER TR SEe aE e WE TE: 
Rana palmipes DIT Trbuslands of fedt 
Zamenis mexican i 
mentovaris 
Coronellamıcrophol 
Rana. montezıunae 
halecina 
pustulosa 
Hypsiglena. 
Spelerpes variegat 
Tropıdonat. melanoq 
Zamenis lineatus 
Scaphiopus duges! 
Tropidonot. chrysoc 
ordinatuıs. 
scalaris 
Amblystoma tgrin. m 
Eumeces lynxe 
Spelerpes chiropterus 
. belli 
Conlia nasus 
Amblyst.altamıranı 
Thorius pernalul 
Spelerpes leprosus 
| 
orizabensis 2 
List €. 
Showing the vertical distribution of 24 Nearetic species. 
Zool, Jahrb. XXIX. Abt. f. Syst. 46 
