396 
RANGE OF HELICID.E: HAPLOGONA. 
only in the most remote regions, often separated by the ocean, 
mountain ranges or desert lands from species of more complex 
organization and greater vigour, their chief 
asylums being the regions furthest removed and 
most difficult of access from the evolutionary 
centre, as the extreme southern extremities of 
Africa, South America, Australia, Tasmania, 
and the more remote equatorial islands of 
the Indo-i\Ialayan region, but their rear is 
closely pressed upon and overlapped by their 
epiphallophorous successors. 
Eastern North America is also stocked by 
numerous species of this very primitive group 
which are there the dominant race, being shielded by the Rocky Moun- 
tain ranges from the intrusion and conq)etition of the more highly 
organized Euadeniate species inhabiting the Pacific slope. 
The Haplogona (utt/Vois, simple; yoi'O'?, seed) are the most lowly of 
the Ilelicidian groups and from the simplicity of their general 
organiz.jxtion are considered to stand near to tlie common progenitor of 
the Ilelicidie and their close allies, and this is 
further emphasized by the exceedingly wide 
distribution their great anti(puty has enabled 
them to attain, as representatives are found 
even in the Arctic regions, but throughout the 
Southern hemisphere the family is met with 
more abundanily, especially in New Zealand, 
Tasmania, the extreme south of South America, 
Southern Australia and South Africa, and is also 
the predominating Helicoid in the oceanic 
islands of Polynesia and elsewhere. 
Ppon continental lands, probably from occu- 
])ying different stations and their habits not 
directly confiicting with the dominant and higher Ilelicidian fauna, 
a few s])ecies of small .size, like onv flelt\r rotundafa, Ilell.r rupei^trts, 
etc., still exist in areas occupied by the most advanced races ; but in 
North America we find the Hajdogona represented by a number of 
fine species occupying the elevated and desert Rocky Mountain region, 
which so effectively divides the invading Euadenia from the much 
weaker, but inedominating, fauna of the eastern states. 
Fig. 728. — Reproductive 
organs representative of the 
Haplogona X 3, Helix 
( Pyramidula ) rotundata 
Miill., Roundhay, Leeds. 
Fig. 727. — Reproductive 
organs representative of the 
Protogona, Helix ( Poly- 
Sdy>‘ei) injlecta Say (after 
Pilshry). 
