GEOGRAPHICAL DISTRIBUTION. 123 
cies of the preceding section extend into this, and almost 
all of those belonging to the next succeeding section are 
common to it ; but it has its otto peculiar species which 
prevail particularly in the mountainous parts of its most 
southerly portion. Among these are Helix spinosa, 
H. major, H. cumberlancHana, H. subplana, H. gularis, 
H. rotula, H. leporina, and H. lasmodon. The physical 
conditions of this section are peculiarly conducive to 
the development of testaceous variation ; hence we find 
here the carinated and heavily-ribbed Helix pattiata, the 
deep-ribbed Helix alternata, and others. In it the 
genera Limax and Tebennophorus are very abundant. 
This section, already distinguished by a larger number 
of peculiar species than either of the others, has been 
but partially explored. Being in its greater part a 
mountainous region, subject to clirnatal influences differ- 
ent from those of the country north of it, it may be 
expected to furnish a still larger number of yet unob- 
served species, and would doubtless well reward the 
industry of any naturalist who should thoroughly recon- 
noitre it. Like the preceding, it extends beyond the 
Mississippi River, but its limits are there unknown. 
Section 4. The Northern interior Section. This 
includes the country between the Ohio River and the 
Great Lakes, and between North Carolina and New 
York and Vermont. Its character is much like that of 
the preceding section, except that its winters are longer 
and more severe. Its boundaries on the north-east and 
north-west are not well denned, and it extends like the 
preceding, west of the Mississippi River. The influences 
