A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554 75
medium length, oblique. Penial ornament a transverse terminal
gland.
DESCRIPTION.—Shell (Figure 28g) ovate to narrowly conic;
height, 2.5-4.0 mm; whorls, 4.5-5.5. Early protoconch
strongly punctate, sculpture weaker on remaining portion.
Teleoconch whorls slightly to moderately convex, sometime
weakly shouldered; sculpture of weak growth lines. Aperture
small, ovate, adnate or slightly separated from body whorl.
Inner lip complete (rarely a thin glaze across parietal wall), thin
to moderately thick; columellar lip sometimes slightly reflected.
Outer lip thin to moderately thick, orthocline.
Umbilicus rimate-perforate. Periostracum light brown.
Operculum (Figure 28/1,0 narrowly ovate, amber, nucleus
highly eccentric; dorsal surface frilled. Attachment scar margin
thickened all around, often broadly so (especially between
along inner edge to nucleus); callus moderate, elongate.
Central radular tooth (Figure Ale) with moderately indented
dorsal edge; lateral cusps, 4-5; central cusp pointed, considerably
broader and longer than laterals; basal cusps, 1 (often
accompanied by weak outer cusp), short, with moderate dorsal
support. Basal process medium width; basal sockets deep.
Lateral margins thickened; neck very weak.
Snout pale to dark brown. Foot, neck pale. Tentacles pale or
gray, with small dark internal pigment patch distal to eyespots.
Opercular lobe with dark internal pigment patch along anterior
edge. Pallial roof, visceral coil light to dark brown.
Ctenidial filaments, 22, medium height and width. Osphradium
centered slightly posterior to middle of ctenidial axis.
Kidney with large (50%) pallial bulge; opening weakly
differentiated. Stomach with prominent triangular caecum
Testis, 2 whorls, overlapping stomach to edge of style sac.
Prostate gland with large (30%) pallial section; pallial vas
deferens with proximal loop. Penis (Figure 52e) large; base
expanded proximally; filament medium length, gently tapered;
lobe about as long as filament, broad, strongly oblique.
Terminal gland small, narrow, transverse, borne along distal
edge of lobe. Filament darkly pigmented internally.
Ovary, 1 whorl, slightly overlapping posterior stomach.
Pallial albumen gland with large (29%) pallial section. Capsule
gland as long as albumen gland. Genital aperture a sub-terminal
slit; vestibule weakly developed. Coiled oviduct a tall, narrow,
vertical loop (strongly kinked near mid-length) slightly behind
pallial wall. Oviduct and bursal duct join well anterior to
oviduct coil and pallial wall. Bursa copulatrix pouch-like, short
(25%), narrow (20%), extending almost to posterior edge of
albumen gland. Bursal duct broad, deeply embedded in
albumen gland, more than three times length of bursa
copulatrix. Seminal receptacle pouch-like, fat, long (60%),
positioned lateral to proximal bursal duct along ventral edge of
albumen gland.
TYPE LOCALITY.—Post-glacial deposit, Goat Island, Niagara
River, New York. Holotype, UMMZ 117363.
DISTRIBUTION.—Michigan, Ohio, Ontario (Canada), Great
Lakes drainage.
REMARKS.—This snail is distinguished from similar P.
scalariformis by its smooth teleoconch, large caecal chamber of
stomach, longer penial lobe; narrowly vertical oviduct coil; and
narrow, sac-like bursa copulatrix positioned entirely lateral to
albumen gland.
MATERIAL EXAMINED.—FSM 91727, creek west of Crescent
Lake, Oakland County, Michigan.
Pyrgulopsis lustrica (Pilsbry, 1890)
Amnicola lustrica Pilsbry, 1890:53.—Baker, 1964:174.
Amnicola lacustris Pilsbry, 1891a:iii [of Index; nomen nudum, probably
misspelling of above].
Amnicola (Marstonia) lustrica.—Baker, 1926:195.—Berry, 1943:29. fig. 3; pi.
1: figs. 4-6; pi. 3: fig. 3; pi. 5: fig. 6.—Robertson and Blakeslee, 1948:84. pi.
X: fig. 11.
Lyogyrus (Marstonia) lustrica.—Thiele, 1928:378.
Marstonia lustrica.—Thompson, 1977:124, figs. 2,4d, 5,16.—Turgeon et aL,
1988:61.
Pyrgulopsis lustrica.—Hershler and Thompson, 1987:29, fig. 5.
Amnicola lustrica gelida Baker, 1921:22.
Marstonia gelida.—Clarke, 1973:247, pi. 21: figs. 7, 8.—Nielsen et al.,
1987:1480.
Amnicola lustrica decepta Baker, 1928:108, fig. 45 [in part].
Marstonia decepta.—Clarke, 1973:244, pi. 21: fig. 6.
Amnicola lustrica perlustrica Baker, 1928:109, pi. VI: figs. 15, 45 [in part].
Amnicola oneida Pilsbry, 1917:46.—Baker, 1964:175.-^Uchardson et al.,
1991:64.
DIAGNOSIS.—Shell ovate- to narrowly-conic, medium to
large-sized, umbilicate. Penial filament short, stubby; lobe
short, oblique. Penial ornament an elongate, usually transverse
terminal gland.
DESCRIPTION.—Shell (Figure 29a) ovate- to narrowly-conic;
height, 3-5 mm; whorls, 4.5-6.0. Early protoconch strongly
punctate. Teleoconch whorls moderate to highly convex;
sculpture of weak growth lines. Aperture ovate, small, adnate
or slightly separated from body whorl. Inner lip complete,
sometimes slightly thickened; columellar lip sometimes
slightly reflected. Outer lip usually thin, orthocline to slightly
prosocline. Umbilicus open. Periostracum olive-gray.
Operculum (Figure 29b,c) ovate, amber, slightly indented
along outer edge; nucleus slightly eccentric; dorsal surface
weakly frilled. Attachment scar margin slightly thickened
along outer edge and between nucleus and inner edge; callus
weak.
Central radular tooth (Figure 41/) with weakly indented
dorsal edge; lateral cusps, 3-5; central cusp rounded, slightly
broader and considerably longer than laterals; basal cusps, 1
(sometimes with weak suggestion of outer cusp), mediumsized,
curved, with moderate dorsal support. Basal process
broad; basal sockets deep. Lateral margins thickened; neck
weak-absent.
Head-foot entirely pale or with light brown tentacles,
light-dark snout, light-moderate brown foot (especially anterior
and posterior edges). Pallial roof uniform brown-black or pale
except for strong black bands along edges of ctenidium and
(sometimes) along dorsal edge of glandular gonoduct (Figure