INSTRUCTIONS FOR COLLECTING MOLLUSKS, AND OTHER USEFUL HINTS FOR 



THE CONCHOLOGIST. 



BY 



Wm. H. Dall. 



Honorary Curator Department of Molhisks, U. S. National Musetim. 

 INTRODUCTORY. 



Invertebrates of the moUuscau type are found in all parts of the 

 world and in nearly every situation. The highest mountains, the 

 widest prairies, the least accessible oceanic islets, and even the desert 

 of Sahara and the frosty moss of Arctic tundras, afford specimens of 

 mollusks on careful and intelligent search. 



For the purposes of the collector the group may be divided into 

 three classes, including, respectively, land, fresh-water, and marine 

 species. Each of these classes requires special treatment and will be 

 discussed seiDarately. Every land area which borders on the sea and 

 contains permanent bodies of fresh water will be found to support 

 representatives of each class. Geologically, each goes back to a remote 

 antiquity. 



LAND SHELLS. 



From the standpoint of the collector this class includes gastropods 

 both of the pulmonate and gill-bearing types, forms which are united 

 in the amphibious Siphonaria, which j)ossesses both gills and a true 

 lung. They may be limpet- shaped or spiral ; operculate or inoperculate; 

 shell-bearing or naked ; herbivorous or carnivorous. 



HABITAT AND STATION. 



They are found at all elevations, from the beaches moist with sea 

 spray to the alpine heights of 14,000 feet in the vicinity of perpetual 

 snow. Some, like Testacella, are subterranean in their habits, pursu- 

 ing earthworms through their burrows and never visiting the light of 

 day ; or nestling in the cancellated recesses of bones in ancient grave- 

 yards {Acicula) where they browse on fungoid mycelium. Others are 

 contented with the protection afforded by dead leaves, decaying logs, 

 under the bark starting from rotting stumps, or in the shelter of loose 

 stones and bowlders. Other groups live on the leaves of sedges, grass, 

 and shrubbery, retreating to the soil for winter quarters ; while in the 



