A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554
field work and laboratory studies was provided by the Smithsonian
Institution Research Opportunities Fund and Abbott
Fund.
The author thanks A. Kabat and two anonymous reviewers
for their comments on this manuscript.
Superfamily RISSOOIDEA Gray, 1847
Family HYDROBIIDAE Troschel, 1857
Subfamily NYMPHOPHILINAE Taylor, 1966b
Genus Pyrgulopsis Call and Pilsbry, 1886
Pyrgulopsis Call and Pilsbry, 1886:9. [Type species, Pyrgula nevadensis
Stearns, 1883; original designation.]
Marstonia Baker, 1926:195. [Type species, Amnicola lustrica Pilsbry, 1890;
original designation.]
Fontelicella Gregg and Taylor, 1965:103. [Type species, Fontelicella
californiensis Gregg and Taylor, 1965; original designation.]
Natricola Gregg and Taylor, 1965:108. [Type species, Pomaliopsis robusta
Walker, 1908; original designation.]
Microamnicola Gregg and Taylor, 1965:109. [Type species, Amnicola
micrococcus Pilsbry in Steams, 1893; original designation.]
Savaginius Taylor, 1966a: 130. [Type species, Paludestrina nanna Chamberlain
and Berry, 1933; original designation.]
Mexistiobia Hershler, 1985:46. [Type species, Mexistiobia manantiali Hershler,
1985; original designation.]
Apachecoccus Taylor, 1987:32. [Type species, Apachecoccus arizonae Taylor,
1987; original designation.]
Yaquicoccus Taylor, 1987:34. [Type species, Yaquicoccus bernardinus Taylor,
1987; original designation.]
DIAGNOSIS.—A North American freshwater genus distinguished
from other Nymphophilinae by combination of small
size, generally ovate to ovate-conic shell, and penis with
relatively few glands.
DESCRIPTION.—Shell globose to elongate-conic or turriform,
1-8 mm tall, with 4-5 whorls. Protoconch flattened to
dome-like, of 1.25-1.50 whorls, near smooth or variably
punctate, often with weak spiral lines on later portion (Figure
1). Teleoconch whorls near flat to highly convex, often
shouldered adapically. Teleoconch sculpture usually only of
fine growth lines and occasional spiral striae, although
periphery of later whorls sometimes strongly angled or keeled.
Aperture near circular to ovate, usually angled adapically.
Apertural lip usually complete and slightly loosened from body
whorl, sometimes adnate, rarely incomplete across parietal
region; columellar lip usually slightly reflected. Inner lip often
slightly thickened; outer lip thinner, usually prosocline.
Umbilicus absent to perforate. Periostracum thin, gray-brown.
Operculum thin to moderately thick, amber-red, paucispiralmultispiral,
with near central to highly eccentric nucleus.
Dorsal operculum near smooth or with whorl outlines frilled;
outer edge usually simple, rarely slightly indented. Ventral
attachment scar margin variably thickened and raised along
portion or entirety of perimeter, attachment area near smooth to
with modest callus.
Well-developed pair of chitinous jaws present. Radula
taenioglossate; ribbon moderately elongate, slightly coiled
behind buccal mass, with numerous (>50) rows of teeth.
Central radular tooth usually trapezoidal, rarely near square,
with well-developed basal process; basal sockets usually deep;
central cusp blunt, rounded or pointed, usually broader and
longer than laterals, often markedly so; lateral cusps, 3-7.
Central tooth with single pair of basal cusps (second, outer pair
rarely present) arising from lateral angles or outer portion of
tooth face. Lateral angles well developed, often thickened,
often with prominent neck along outer edge. Lateral teeth with
prominent central cusp flanked by 2-6 smaller cusps; marginal
teeth with 14-37 fine cusps, usually more numerous on outer
tooth. Stomach chambers about equal in length. Posterior
caecum absent to prominent. Rectum without bend or coil in
pallial roof. Anus positioned near mantle edge.
Animal pigmentation ranging from pale, except for black
eyespots, to uniformly dark brown-black. Epithelial melanic
pigment usually prominent on head/foot, pallial roof, visceral
coil. Pallial roof pigmentation uniform-diffuse; or of 2-3
narrow-broad bands, extending along sides of ctenidium and
(sometimes) dorsal edge of pallial gonoduct and often uniting
over pericardium (Figure 2e).
Snout slightly longer than broad, with prominent distal lips.
Cephalic tentacles extending beyond tip of snout, with little or
no taper distally; tentacle tips rounded. Dorsal tentacle ciliation
varying from small, scattered patches to one or more prominent
longitudinal bands; weak transverse ciliation sometimes present
along side of left tentacle (Figure 3). Foot large, rounded
posteriorly, truncate anteriorly.
Ctenidium usually filling most of length of pallial cavity;
filaments, 10-35, generally broadly triangular. Osphradium
usually short, narrow, centered slightly posterior to middle of
ctenidial axis. Kidney usually with prominent pallial bulge;
kidney opening simple or slightly thickened and whitened.
Hypobranchial gland weakly developed in posterior pallial
roof.
Gonads usually simple lobate, often occupying at least one
whorl and at least the posterior stomach chamber. Prostate
gland bean-shaped to fan-like, usually with small to prominent
pallial component, rarely positioned entirely posterior to pallial
wall. Anterior vas deferens exiting from anterior portion of
prostate gland (proximal to tip); pallial vas deferens usually
with proximal twist or bend. Penis (Figure 2a-d) originating
well behind right cephalic tentacle; generally large, extending
beyond edge of mantle and as wide as or wider than snout Base
of penis square to broadly rectangular, distal penis usually
bifurcate, with distal lobe and penial filament. Filament usually
narrow, tapering, variable in length, rarely longer than base of
penis, usually horizontal to slightly oblique (to right), rarely
highly oblique. Lobe small and slender to broadly rectangular
(as long as base), horizontal or (rarely) oblique (to left), rarely
absent. Penial vas deferens slender, coursing straight along