DISTRIBUTION OF GENERA AND SPECIES. 173 
and temperate portions of the American continent and 
islands, their place being supplied by the genera Teben- 
nophorus and Vaginulus, the first in North and the 
second in South America, the Antilles and that part of 
Florida adjacent to Cuba. The only exception to this re- 
mark is, a single and somewhat doubtful species of Limax, 
common in the United States. 1 At the same time, the 
climate is favorable to several species of foreign origin, 
which are rapidly spreading through the country. Vit- 
rina only appears in America north of 44° north latitude. 
Helix, a genus common to all the continents and large 
islands, is most abundant in temperate latitudes of the 
northern hemisphere, towards their southern limits, and 
gradually diminishes in the number of its species, both 
in approaching the equator, and in going into higher 
latitudes. Bulimus affects mostly the inter-tropical lat- 
itudes, where it takes the place of Helix, while in the 
temperate latitudes of North America and of the east- 
ern continent it is reduced to a very small number of 
species. In South America, however, which seems to 
be the great numerical centre of the genus, the species 
abound as far as 25° south latitude. The European form 
of Pupa, differing however in specific characters, is 
common to North America, and extends in a few species 
1 The territory belonging to the United States, on the Pacific Ocean, south 
of 49° north latitude, is also known to produce one or more species of 
Limax, drawings of which were made by the artists of the United States 
Exploring Expedition. We do not know whether the species have been 
determined or not. 
vol. I. 45 
