﻿112 PROCEEDINGS OF THE NATIONAL MUSEUM touios 



Fla., and kindly forwarded them to the United States National Mu- 

 seum. A few weeks later I was sent to this spring to determine its 

 prevalence, manner of introduction, and its possible spread. 



Thiara granifera is present in the main Lithia Spring in extraordi- 

 nary numbers, sometimes as many as 400 specimens per square foot. 

 A small, connecting subsidiary spring contains a few larger individ- 

 uals. A fuller account of the spring condition appears in the section 

 on bionomics (p. 100). 



An aquatic-plant and fish dealer in Tampa related that he acquired 

 specimens in 1937 while on a visit to California. Since that time, 

 his plant vats have been stocked with this moUusk which, as an oddity, 

 had been sold over a hundred times in a year as the "Philippine horn 

 of plenty." It was his opinion that the snails were probably acci- 

 dentally introduced to the spring around 1940, when improperly 

 washed tubs were used to gather native plants. I have seen specimens 

 in home aquaria in Silver Spring, Md., which had been acquired 

 from Washington, D. C, dealers. 



It will be seen by the above experiences that any foreign snail 

 that has sales value because of its attractive appearance or peculiar 

 habits will soon be distributed to many parts of the country and in 

 many cases will be introduced purposely or accidentally to native 

 waters. Probably the most likely solution to the problem of con- 

 trolling introduced, dangerous moUusks lies in encouraging dealers, 

 particularly the importers, to send their moUusks for identification 

 to musemns that have specialists in mollusks on the staff. The present 

 programs of the Bureau of Plant Quarantine and Insect Control and 

 the United States Public Health Service appear to be extensive enough 

 for our protection. It must be realized that even the most stringent 

 of laws prohibiting the import of foreign mollusks are not going to 

 offer perfect screening, since accidental introductions by various means 

 are likely to occur. In the past hundred years approximately 50 

 species of exotic species of land and fresh-water mollusks have estab- 

 lished themselves in the United States and Canada. 



The geographical origin of these snails will probably remain un- 

 certain. From the condition and size of individuals in the Lithia 

 Spring colonies, it appears that an abnormally stunted ecological form 

 exists, which makes fair comparisons with races from endemic Pacific 

 areas difficult. The more closely resembling lots in the United States 

 National Museum are from the Hawaiian and Marianas Islands. 

 They are possibly members of the subspecies or geographical race 

 Thiara granifera niauiensis Lea, 1856. 



It is highly unlikely that this snail will spread to many other sec- 

 tions of the United States, except in rare spring localities where water 



