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THE POPULAR SCIENCE MONTHLY 



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Desert Snails Aestivating in the Twisted Trunk of a Desert Tree. Mangrove 



Seeds. 



conical pits of ant lions often covered the ground so thickly that it was 

 impossible to avoid walking on them. 



Once near the sea we came across a great number of terrestrial hermit 

 crabs, Cenobita diogenes, each encased in the shell of a land snail. The 

 little army was moving slowly through a rocky portion of the desert 

 where its members could sidle quickly from the shelter of one rock to 

 that of another. These little crabs live a truly terrestrial life, and return 

 to the ocean only once a year, when they breed. They apparently require 

 very little water, for I brought three home with me and they have lived 

 in a dish of dry sand in my office for more than six months. They have 

 of course been supplied with food and a small cup of drinking water. 



This desert, like those in other parts of the world, has a rather sparse 

 fauna consisting of a few species, most of which are able to stand extreme 

 desiccation, long fasts and great heat. The lizards and tortoises with 

 their dry, scaly skins, the land hermits with thick exoskeletons and 

 borrowed shells, the land snails with thick calcareous coverings, are all 

 admirably suited to desert conditions. 



Brooks and Eivers 



The streams on the northern Colombian coastal slope are easily 

 divisible into two classes — mountain torrents and rather slow-flowing 

 meandering rivers. From headwaters in the mountains the water rushes 

 down over rocky beds for a time, then comes abruptly to the level sandy 

 plain where much of its impetus is soon lost. 



The most striking characteristic of the animals of the mountain tor- 

 rents is their ability to hold on. The little catfish found there have a 



