Pulmomfera of Elaine. 49 



From the foregoing catalogue, it will be seen that thus far, 

 forty-nine species of terrestrial, and fifty-five species of fluviatile 

 mollusca have been detected in the State ; as a consequence how- 

 ever of its geological formation which is made up chiefly of azoic 

 rocks, covered with extensive tracts of coniferous trees, the land 

 mollusks do not occur in that profusion which characterizes the 

 faunas of many other States ; for it is well known that the presence 

 of coniferous trees, exerts a retarding influence on the growth and 

 increase of the land pulmonates ; and, on the contrary, that hare], 

 wood growths and calcareous soila are most congenial to their ex- 

 istence and perpetuation. The meagerness of the soil, and the 

 general prevalence of pine forests, must therefore in a measure 

 account for the absence of several species occurring farther west, 

 and ai-e certainly the cause of that scarcity of individuals which 

 truly characterizes the molluscan fauna throughout this State. It 

 is believed that when our unexplored districts at the north are 

 carefully investigated many forms new, either to the State or to 

 science, will be revealed. 



It is interesting to compare the Increase made from time to 

 time, in the species enumerated in the few catalogues of Maine 

 shells, which have been published, ^vith the number catalogued 

 in this paper. 



Land. Freshwater. Total. 

 1836. Jackson^'s Report Geology of Maine, 3 



1841. Mighels' first catalogue, IG 



1842. Mighels' second catalogue, 2*2 

 1864, This catalogue, 49 55 104 



We give below a table showinsc the number of laud and fresh 

 water species of Mollusks in England, Scotland and Ireland for 

 comparison with those of Maine, It will be seen that while the 

 land sjie-cies outnumber the fresh water species in Britain, it is quite 

 the revei-se in Maine. In Britain also we have several genera of 

 iand mollusks which do not occur in Maine, such as Cyclostoma, 



«r«UENAL P, S. N. H, 4 MAECH, 1864. 



