A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554
Pyrgulopsis merriami (Pilsbry and Beecher, 1892),
new combination
Fluminicola merriami Pilsbry and Beecher in Pilsbry, 1892:143; 1899:123.—
Stearns, 1893:281, fig. 2; 1901:286, fig. 5.—Walker, 1918:142.—Morrison,
1940:124.—Baker, 1964:174.—Burch, 1982:22, fig. 146.—TVirgeon et al.,
1988:60.—USDI, 1991b:58819.
Fluminicola (Heathilla) merriami.—Hannibal, 1912b:188.
"Fluminicola" merriami.—Taylor, 1975:122.
DIAGNOSIS.—Shell globose, medium-sized, umbilicate. Penial
filament short, lobe medium length. Penial ornament of
three penial glands, small Dg3 on tubercle; and curved,
horizontal terminal gland.
DESCRIPTION.—Shell (Figure I9d) globose; height, about 3
mm; whorls, about 4. Early protoconch moderately punctate,
sculpture weaker in later portion. Teleoconch whorls moderately
convex, distinctly shouldered, with shallow sutures;
sculpture of strong growth lines and weak spiral striae.
Aperture ovate, large, narrowly adnate to or (rarely) slightly
separated from body whorl. Inner lip complete, thickened in
columellar region. Outer lip prosocline. Umbilicus deeply
perforate. Periostracum light brown.
Operculum (Figure \9e,J) broadly ovate, very light amber,
nucleus slightly eccentric; dorsal surface frilled. Attachment
scar margin moderately thickened along inner edge near
nucleus, otherwise smooth; callus moderate.
Central radular tooth (Figure 376) with moderately indented
dorsal edge; lateral cusps, 5; central cusp pointed, slightly
longer than laterals. Basal cusps, 2, very short (outer cusp more
so), narrow, with weak dorsal support. Basal process wide;
basal sockets deep. Lateral margins thickened; neck very
pronounced.
Cephalic tentacles pale except for dark internal pigment
patches distal to eyespots. Snout and foot pale to moderate
brown. Opercular lobe, neck usually pale. Pallial roof, visceral
coil light to dark brown-black.
Ctenidial filaments, about 27, tall, narrow. Osphradium
centered posterior to middle of ctenidial axis. Kidney with
small bulge into pallial cavity (16%); opening slightly
thickened. Stomach with narrow caecum.
Testis, 1.5 whorls, overlapping posterior stomach chamber.
Prostate gland a broad bean shape, with short pallial section.
Pallial vas deferens with proximal kink. Penis (Figure 48fc)
large; filament short, broad; lobe large, broad. Penial glands
consisting of two units covering most of filament (one each on
dorsal and ventral surfaces; sometimes fused distally), and
much smaller unit between the above along dorsal edge
proximally. Dg3 on small raised tubercle, sometimes borne
along edge of lobe or slightly onto ventral surface. Terminal
gland elongate, curved, usually horizontal, overlapping both
dorsal and ventral surfaces. Ventral gland large, sub-terminal,
stalked, usually positioned right of mid-line; second, very small
gland sometimes present lateral to above. Filament unpigmented.
Ovary, 1 whorl, overlapping posterior stomach chamber.
Albumen gland without pallial section. Capsule gland as long
as albumen gland. Ventral channel tall; genital aperture a
terminal broad pore without vestibule. Coiled oviduct a slight
horizontal twist followed by broad horizontal loop filling much
of albumen gland (and partly overlapping bursa copulatrix).
Oviduct and bursal duct join just behind pallial wall. Bursa
copulatrix ovoid, almost as long and as wide as albumen gland,
with most of length (75%) posterior to albumen gland. Bursal
duct broad, short Seminal receptacle pouch-like, fat, short,
overlapping anterior bursal copulatrix, extending to posterior
edge of albumen gland.
TYPE LOCALITY.—A warm spring (temperature 97° F. [36°
C.]) in Pahranagat Valley [Lincoln County], Nevada. It is not
clear from narrative accounts of the Death Valley Expedition,
nor from the map showing the expedition route, which
particular spring in Pahranagat Valley was visited. There are
several thermal springs in the valley (Garside and Schilling,
1979): Ash Springs (T6S, R60E, NE1/4 sec. 1) harbors a
hydrobiid population closely conforming to merriami in shell
features and probably is the type locality. (Other large thermal
springs along the basin floor contain another species that does
not closely resembly merriami.) Lectotype (Baker, 1964:174),
ANSP 67278; paralectotypes, ANSP 27782; USNM 123626.
DISTRIBUTION.—Known only from presumed type locality
in Pahranagat Valley, which presumably drained to the
Colorado basin in late Cenozoic pluvial periods (Hubbs and
Miller, 1948).
MATERIAL EXAMINED.—USNM 873163 (presumed topotypes).
Pyrgulopsis metcalfi (Taylor, 1987), new combination
Fontelicella metcalfi Taylor, 1987:12, fig. 5.
"Fontelicella" metcalfi.—USDI, 1991b:58819.
DIAGNOSIS.—Shell ovate to narrowly-conic, medium-sized,
narrowly umbilicate. Penial filament and lobe medium length.
Penial ornament an elongate penial gland, oblique Dgl, oblique
Dg2, small Dg3 borne on weak swelling; elongate, slightly
curved, transverse terminal gland, and ventral gland.
DESCRIPTION.—Shell (Figure \9g) ovate- to narrow-conic;
height, 2.0-2.7 mm; whorls, 3.5-4.5. Early protoconch weakly
punctate, later portion with weak spiral lines adapically.
Teleoconch whorls moderately convex, shouldered; sculpture
of moderate growth lines. Aperture ovate, adnate or slightly
separated from body whorl. Inner lip complete, thickened;
columellar lip slightly reflected. Outer lip slightly prosocline,
weakly sinuate. Umbilicus narrowly rimate, shallow. Periostracum
light tan.
Operculum (Figure \9h,i) narrowly ovate, light amber
(darker in nuclear region); nucleus slightly eccentric; dorsal
surface weakly frilled. Margins of attachment scar moderately
thickened between nucleus and mid-point of inner edge. Callus
broad, thickened near nucleus.
Central radular tooth (Figure 37c) with moderately indented
dorsal edge; lateral cusps, 5; central cusp pointed, considerably
broader and longer than laterals; basal cusps, 1, (second very
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