A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554 59
REMARKS.—The small size and ovate shape of these empty
western shells suggest membership in Pyrgulopsis. This
species is distinguished from Pyrgulopsis brandi, which was
described from extant populations occurring in the same
region, by its squatter shell and thin apertural lip.
Pyrgulopsis pecosensis (Taylor, 1987), new combination
Fontelicella pecosensis Taylor, 1987:27, fig. 12.
"Fontelicella" pecosensis.—USDI, 1991b:58819.
DIAGNOSIS.—Shell ovate- to narrowly conic, medium-sized,
umbilicate. Penial filament short; lobe short, broad. Penial
ornament a short Dgl, small Dg3 borne on lobule; curved,
elongate, transverse terminal gland; and ventral gland.
DESCRIPTION.—Shell (Figure 23a) ovate- to narrowly conic;
height, 2.0-2.9 mm; whorls, 4-5. Early protoconch weakly
punctate, otherwise near smooth except for faint spiral lines.
Teleoconch whorls moderately convex, sometimes weakly
shouldered; sculpture of weak growth lines and occasionally
weak spiral lines. Aperture ovate, angled above, usually adnate
to body whorl. Inner lip complete, thickened; columellar lip
sometimes slightly reflected. Outer lip thinner, prosocline.
Umbilicus shallowly rimate or perforate. Periostracum tan.
Operculum (Figure 23b,c) ovate, amber, darker in nuclear
region; nucleus slightly eccentric; dorsal surface strongly
frilled. Attachment scar margin broadly thickened between
nucleus and inner edge (extending slight distance along edge),
otherwise very weak-smooth; callus weak.
Central radular tooth (Figure 38i) with moderately indented
dorsal edge; lateral cusps, 6-7; central cusp rounded, considerably
longer and broader than laterals. Basal cusps, 1, short, with
slight dorsal support. Basal process narrow; basal sockets deep.
Lateral margins thickened; neck pronounced.
Cephalic tentacles, snout moderate-dark brown. Tentacles
sometimes with central unpigmented streak. Foot lightly
pigmented except for darkened anterior and posterior edges.
Opercular lobe with darkened edges. Neck pale. Pallial roof,
visceral coil dark brown-black.
Ctenidial filaments, 15-20, medium height and width.
Osphradium positioned centrally to slightly posterior to middle
of ctenidial axis. Kidney with prominent bulge (up to 40%) into
pallial cavity; opening thickened. Stomach with medium-sized
triangular caecum.
Testis, 1.5-2.0 whorls, overlapping stomach to edge of style
sac. Prostate gland bean-like, strongly recurved, with large
(25%) pallial section; pallial vas deferens with gentle proximal
bend. Penis (Figure 49/) large; filament short, narrow; lobe
short, broad. Dgl short, extending along right edge slightly
onto base of filament; Dg3 a small tubercle (sometimes absent)
borne on pronounced distal lobule. Terminal gland elongate,
transverse, curved, largely ventral. Ventral gland small,
sub-terminal, borne on low swelling. Filament darkly pigmented.
Ovary, 1 whorl, overlapping posterior stomach chamber.
Pallial albumen gland short, sometimes absent. Capsule gland
shorter than albumen gland. Genital aperture a terminal broad
pore without vestibule. Coiled oviduct of tight posterior
oblique coil followed by (and overlapping) broad horizontal
loop, positioned near middle of albumen gland. Oviduct and
bursal duct join well posterior to pallial wall. Bursa copulatrix
ovoid, elongate (up to 67%), broad (67%), with much of length
(67%) posterior to albumen gland. Bursal duct medium length
and width. Seminal receptacle finger-like, short, positioned
alongside anteriormost bursa copulatrix and/or proximal bursal
duct.
TYPE LOCALITY.—Blue Spring, center SW1/4 sec. 27, T
24S, R 26E, Eddy County, New Mexico.
DISTRIBUTION.—Pecos River drainage, southeastern New
Mexico.
REMARKS.—This species appears more closely related to
northern congeners (P. hendersoni, P. idahoensis, P. robusta)
than to local species. It differs in its smaller size, superficial
position of Dgl, anterior position of seminal receptacle, and
location of seminal receptacle along ventral edge of albumen
gland.
MATERIAL EXAMINED.—USNM 873131 (topotypes).
Pyrgulopsis perturbata Hershler, 1989
Pyrgulopsis perturbata Hershler, 1989:189, figs. 26e-g, 33-36.
DIAGNOSIS.—Shell ovate to low conical, medium to largesized,
narrowly umbilicate. Penial filament short, lobe medium
length. Penial ornament a small Dgl, transverse terminal gland,
and ventral gland.
DESCRIPTION.—Shell (Figure 23d) ovate to low conical;
height, 2.7-4.0 mm; whorls, 4.25-5.0. Early protoconch very
weakly punctate, otherwise near smooth. Teleoconch whorls
slightly convex, sometimes shouldered; sculpture of very faint
growth lines. Aperture broadly adnate to very slightly separated
from body whorl. Inner lip complete, usually thick; columellar
lip well reflected. Outer lip thick, slightly prosocline. Umbilicus
rimate. Periostracum tan.
Operculum (Figure 23