Key to Terrestrial Gastropods
of British Columbia
- 47a
- Major axial sculpture of more or less regularly
spaced grooves, with smooth, flattened, raised areas between (see
figure below) - 48
- 47b
- Shell smoothish or with axial sculpture not as
above - 49
Cross-section
(perpendicular to the axial grooves) of the shell wall of Nesovitrea
showing characteristic grooves and flattened areas between.
- 48a
- Shell nearly colourless with a greenish tinge
and smaller, 3.5-4.3 mm (3½-4½ whorls) - Nesovitrea
binneyana (Figure)
- 48b
- Shell amber-coloured and larger, 4.6-5.2
mm (3½-4 whorls) - Nesovitrea
electrina (Figure)
- 49a
- Shell with widely and more or less regularly spaced
(at least on the whorls of the spire), sharply angular or lamellar
axial ribs - 50
- 49b
- Shell smoothish or with axial sculpture
closely and either regularly or irregularly spaced - 55
- 50a
- Shell white, grey or yellowish grey - 51
- 50b
- Shell yellowish brown, brown or reddish
brown - 53
- 51a
- Lip flared but thin - 52
- 51b
- Lip at least slightly thickened - Vallonia
gracilicosta
- 52a
- Shell width to about 2.2 mm - Vallonia
cf. perspectiva (Figure)
- 52b
- Shell width 2.5-3.4 mm - Vallonia
cyclophorella (Figure)
- 53a
- Spire almost flat - Planogyra
clappi
- 53b
- Spire moderately raised - 54
- 54a
- Umbilicus about 20-25% of the width of the shell;
protoconch initially smooth, then with rather widely spaced spiral
striae - Paralaoma caputspinulae
- 54b
- Umbilicus larger, greater than 30% of the
width of the shell; protoconch smooth - 36
- 55a
- Lip thickened within by a callus - 56
- 55b
- Lip not thickened within - 57
- 56a
- Last whorl near the aperture distinctly increasing
in width much more than previously; outline of the shell ovate;
umbilicus elongate, elliptically spiral; outer lip gradually expanded,
not at a right angle - Vallonia
excentrica (Figure)
-
Introduced
to British Columbia (Forsyth
in press)
- 56b
- Last whorl near the aperture increasing
in width only a little more than previously; outline of the shell
almost circular; umbilicus regularly spiral; outer lip abruptly
flared outward at a right angle Vallonia
pulchella (Figure)
Introduced to British Columbia (Forsyth
in press)
- 57a
- Whorls rapidly enlarging; umbilicus minute - Vitrina
pellucida (Figure)
- 57b
- Whorls enlarging more slowly; umbilicus
about 15-30% of the width of the shell - 58
- 58a
- Shell whitish or colourless - 59
- 58b
- Shell yellowish, yellowish brown, brown
or reddish brown - 63
- 59a
- Umbilicus about 15% of the shell width - Vitrea
contracta
Introduced to British Columbia (Forsyth
in press)
- 59b
- Umbilicus about 25-30% of the shell width
- 60
- 60a
- Axial sculpture of fine, close riblets - Striatura
pugetensis
- 60b
- Axial sculpture more or less non-existent;
fine incremental striae only - 61
- 61a
- Umbilicus about 30% of the shell width; spire
moderately elevated - Hawaiia minuscula
- 61b
- Umbilicus about 25% of the shell width;
spire very low - 62
- 62a
- Width 4-5 mm; 5-5¼ whorls; SE British Columbia
- Microphysula
ingersolli (Figure)
- 62b
- Width 3.6-4.4 mm; 4-4½ whorls; Coast
and Cascade Mountains and Vancouver Island Range - Microphysula
cookei
- 63a
- Whorls rapidly enlarge in width: last whorl at
least twice the width of the penultimate whorl one-half coil back
from aperture - 64
- 63b
- Whorls less rapidly enlarge in width: last
whorl one-half coil back from aperture last whorl less than twice
the width of the penultimate whorl - 65
- 64a
- Axial sculpture of fine, close riblets; protoconch
with minute, close spiral striae; shell width to 1.7 mm (2¾-3
whorls); width of umbilicus about 30% of the width of the shell
- Striatura pugetensis
- 64b
- Axial sculpture weak and shell almost smooth;
protoconch smooth; shell width greater than 5 mm (5-6 whorls);
width of umbilicus about 17% of the width of the shell - Oxychilus
alliarius
Introduced to British Columbia (Forsyth
in press)
- 65a
- Shell width up to 1.4 mm or 1.8 mm (3½-4½
whorls) - P.
californicum & Punctum randolphii
P. californicum is generally slightly larger than P. randolphii.
- 65b
- Shell larger - 66
- 66a
- Aperture narrow and crescent-shaped - 67
- 66b
- Aperture broader, more rounded - 68
- 67a
- Umbilicus tiny, pit-like - Euconulus
fulvus (Figure)
- 67b
- Umbilicus larger, about 10% of the width
of the shell - Pristiloma
chersinella (Figure)
- 68a
- Animal bluish grey on tentacles and on back, lighter
on sides and tail; shell width 5-6 mm (4½ whorls); shell
with faint and extremely fine, microscopic spiral striae; generally
inhabiting drier areas than the next species - Zonitoides
arboreus (Figure)
- 68b
- Animal blackish; shell width 6-7 mm (4½
whorls); microscopic spiral striae absent; generally inhabiting
marshy areas - Zonitoides
nitidus (Figure)
The spiral striae present on the shell surface of Z. arboreus
are exceptionally fine. They should be looked for, using reflective
light and a minimum of 30× magnification, between the larger
axial riblets; however, not all specimens show striae clearly,
even at this magnification, and in some specimens striae are apparently
absent. Pigmentation of the animal is the most reliable distinguishing
feature and should be used whenever known. Zonitoides arboreus
is characteristically more depressed and with a wider umbilicus
than Z. nitidus.
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