VARIATION IN BANDING. 
97 
the progress of gi’owth, the banding being usually isolated and 
distinctly separate in youth anrl tending to become transversely 
combined at the margin of the aperture on approaching maturity. By 
this method a distinctive or special number 
is applied to each of the five bands found 
in the typical form of Tleli.r vemnrali>t, or 
other species of the Pentatmniate grouj), 
according to the position it occupies ou the 
shell, the uppermost or one nearest the 
suture being the first, and the lowermost 
or one nearest the umbilicus the fifth, the type form, which has always 
five distinct bands, being expres.sed by the formula 12345 (see f 1 95). 
If a band is suppressed or absent, this is shown by the use of a 
cypher 0 instead of its number; thus the 
formula 12045 would signify that the 
first, second, fourth, and fifth bands 
were present, and the cypher in its 
appropriate position would indicate the 
absence of the third band (see f 19G) ; 
if, however, the whole of the five bands 
are absent and the shell be therefore 
practically unicolourous from showing 
only the ground tint, then this phase of 
variation is expressed by the use of 
five cyphers 00000 iu lieu of the appro- 
priate numbers (see fig. 197). 
The coalescence or fusion of the band- 
ing is indicated by enclosing in paren- 
theses, or by some other method which 
will clearly show the peculiarity, the 
numbers representing those bauds which 
are united together, thus the formula 
(12)3(45) would signify that the first 
and second bands were united, and also 
the fourth and fifth, the third only being free or isolated (see f. 1!)S). 
When, however, the whole five bands are [iresent and united 
together, presenting the appearance of one excessively broad baud 
occupying nearly the entire surface of the whorl, and therefore only 
Fk;. 19S . — IIcUx iicuioralis L., 
formula (12) 3 (lo), 
Piperstown, co. Louth, 
Collected by Kliss S. Smith. 
Fig. 197 - — IfcUxncmoralis L., 
formula 0001)9, 
Isle of Lismore, Argyll, 
Collected by Mr. A. Somerville, 
P.Sc., F.L.S. 
Fig 19f>. — Helix 7ti'i)iorali^ L. 
formula 12015, 
lUtton, near Path, 
Collected by Miss F. M. Helc. 
Fig. 195 . — Helix ^leitwralis L. 
type formula 12345, 
Litton, near Path, 
Collected by Miss F. .I\I. Hele. 
