3‘U 
RANGE OF HELICID.E: BELOGONA. 
Fig. 724. — Reproductive or- 
gans representative of the 
Relogon.a Siphonadenia, Helix 
{ rachca) hortensis MiilL, York. 
Tlie Belogona Sipliouadeuia an arrow ; yoi'o?, seed ; a-iffiov, 
tube ; dSijr, a gland) of Pilsbry, tire most bigldy developed Helices 
ui)oii the globe, are tyi)ically distinguished by a well-developed dart 
apparatus and digitiform vaginal mucus 
glands, characters which culminate in the 
subsidiary group Pentatmnia (irevTiL, five ; 
TuivLu, a fillet or band), of which our ffeli.r 
nemor(iIl.<, lleli.v etc., are examples. 
This group is especially characteristic of 
the European region, where the most highly 
organized of the group are found, the more 
ancient and morphologicall}' less perfect of 
the .siphonadeniate fitrms, as Frnticicoht, 
IF/iomitix'n, etc., which being early evolved 
are more widely .spread, constituting the 
advance guard of the new group, and have 
already spread over the Mediterranean 
sub-region and i)artially acro.ss Asia, intermingling with the rear of 
the retreating Euadeniate race, whom the}' have supjdanteil and 
driven otf from the North Central European area, in which the 
Euadenia were formerly ])redominant. 
'I'he Ihdogona Euadenia (/ieA.o?, an arrow ; yoi'os', seed ; ey well ; 
a gland) are a less highly organized grou}), ])os.sessing a simpler 
dart apparatus and sacculate mucus glands upon the dart sac. Tins 
group attains its greatest and most 
characteristic deveinpment in Eastern 
Asia, the genus llr/icoxfpla, with its 
primitive dart apparatus, constituting its 
advanced guard in the old w(jrld, having 
])enetrated to the tropical islands of the 
Indo-Malayan region ; this group, how- 
ever, still exists in the ^lediterranean 
region and in Central Asia, mingling 
with, but retiring before, the advancing 
kSiphonadeniate forms, the Euadeniate 
.sj)ecies being now expelled from the 
chief evolutionary area, except for the 
degenerate He/ i, r /niftnim, which still lingers on Central European 
soil, the solitary repre.sentative there of this formerly dominant race. 
representative of the Belogona Kua- 
(lenia, Helix {^Epi f>hragiiiopho^n'S 
tyaski var. caya/nacensis Hemphill 
(after Pilsbry). 
