CHAPTER XIT- 
REPTILES, BATRACHIANS AND FISHES—BY A. DE C. SOWERBY. 
N these branches of the Biological work of the Expedition comparatively 
little was done chiefly because there was so little to collect. North China 
is very poor in cold-blooded vertebrates and the whole collection included not 
more than sixteen species, which were presented by Mr. Clark to the U.S. 
National Museum. 
The explanation for this can be expressed in three words: unfavourable 
climatic conditions. 
In the first place the excessive cold of the North China winter tells very 
severely against snakes and lizards. For three months the thermometer 
nightly registers from twenty to forty degrees of frost. The ground is frozen 
hard as arock to a depth of several feet. Rivers and lakes are covered with 
layers of ice from two to four feet thick, whilst marshes and mountain streams 
become solid. 
Following the severe winter frosts, comes a long period of drought lasting 
through the spring into early summer. Sometimes this drought is prolonged 
through the whole of the latter season. This terrible dryness is very hard on 
batrachians, especially as it usually occurs during the spawning season, when 
they need water most. Apart from one or two small varieties, fish do not 
exist, except in permanent streams, rivers or lakes. 
There is litthke wonder then, that North China boasts so few species 
belonging to these classes of vertebrates. As was shrewdly remarked about 
them, they have to hibernate in winter and aestivate in summer. 
Reptiles. 
On the present expedition three species of snakes only were secured. 
The commonest of these was the olive water-snake (T7ropidonotus tigrinus), a 
beautiful reptile of a bright sap-green colour. On the throat are patches of 
orange red which extend down either side of the body, growing smaller till 
109 
