YUKKSHlRh; NATl llA LISTS UNlUN. 
expelled from the N(jrtlierii Heuiisplieie in the Old World by the 
pressure of the more advanced forms which have successively followed 
them, so that they now exist only in the most remote regions ; 
their chief sanctuaries being regions furthest removed and most 
dithcult of access from the evolutionary centre ; these refuges are 
the southern portions of Africa, Australia, and Tasmania, and the 
more rennjte islands of the Indo-Malayan region. 
This primitive group also apparently crossed the Behring bridge 
and travelled southwards, probably by a similar path to that trodden 
by the various races which successively followed them ; on reaching 
Central America they ()vers])read the whole of the West Indian 
Islands, and invaded the United States by way of the Floridan 
peninsula, occupying the whole of the Alleglianian region and the 
basin of the Mississippi river; while others continued on their way 
from Central America and entered South America, penetrating 
into the Argentine, and beyond the i)oint as yet leached by the 
Epiphallogona. 
The Haplouona are the most generalized and lowly of the 
Helicidian groups: they are not strictly Helices, but Helicoids of 
the simplest organization, and probably stand near the ])r()bable 
common ancestor of the Helicidian group. Their consec^uent 
immense antiquity is confirmed by the exceedingly wide distribution 
this has enabled them to attain, as representatives are found in the 
most remote and in the most inclement regions. 
This group was, probably, the first of living Ilelicida' to arise, and 
their place of origin was, probably, the same as that of the preceding 
groups ; and though myriads of ages have elapsed since the group 
was dominant in Europe, where it is now only represented by a few 
species of the most minute size, it attains, in the weaker southern 
hemis])here, a great development, being more or less abundant in 
New Zealand, Tasmania, South Australia, South Africa, and its 
members are to-day the ])redominating Helicoids in the oceanic 
islands of Polynesia and elsewhere. 
The Haplogona were, probably, the first to cross the Aleutian land- 
bridge from x\sia into North America, and in all probability travelled 
by the path which their successors afterwards followed ; they passed 
in advance of the Protogoua, along the Pacific coast, overspreading 
the West Indian Islands, and entering the Eastern United States, 
followed by the Protogona, which have since compelled the bulk of the 
Haplogonous species to occupy the elevated and barren region lying 
between the Rocky Mountains and the Sierra Nevada and Cascade 
M(juntains, where, freed from the competition of more advanced 
grou])s, a number of fine and large species have become developed. 
Others passed forward through Central America into South 
America, and have been driven to now occupy the extreme southern 
extremity of that continent, beyond the point where any of the 
later developed and more dominating species have as yet penetrated. 
