A Review of the North American Freshwater Snail Genus Pyrgulopsis

eviewed (as Marstonia) by Thompson (1969, 1977), for sake
of completeness and to add additional morphological details
where necessary. Recent species incorrectly assigned to
Pyrgulopsis in the literature are listed, for the reader's
convenience, in Appendix 1. Fossils largely have been
excluded from consideration owing to the difficulty of
assigning empty shells to hydrobiid genera, but those species
described as or previously allocated to Pyrgulopsis (or junior
synonyms thereof) are listed in Appendix 2.
MATERIALS AND METHODS.—Pyrgulopsis species were
characterized based on examination of type and other dry
museum material (principally USNM) as well as anatomical
study of topotypes and/or other specimens as available.
Anatomical material used to characterize species are listed in
the "Material Examined" sections. Institutional repositories of
examined specimens are indicated by the following abbreviations:
ANSP Academy of Natural Sciences, Philadelphia
CAS California Academy of Sciences, San Francisco
FSM Florida Museum of Natural History, Gainesville
LACM Los Angeles County Museum of Natural History
MCZ Museum of Comparative Zoology, Harvard University,
Cambridge
SBMNH Santa Barbara Museum of Natural History
UCM University of Colorado Museum, Boulder
UIMNH University of Illinois at Urbana-Champaign Museum of
Natural History
UMMZ University of Michigan Museum of Zoology, Ann Arbor
USNM former United States National Museum, collections now in
National Museum of Natural History, Smithsonian Institution,
Washington, D.C.
UTEP University of Texas at El Paso
Anatomical study was of alcohol-preserved snails that had
been relaxed with menthol crystals and fixed in dilute (4%)
formalin. Examination of live animals, while especially
desireable for accurate description of head-foot features such as
size and shape of cephalic tentacles and snout, was limited
given the broad scope of this project and logistical difficulties
inherent in setting up field laboratories. Alcohol material, when
properly prepared, nevertheless is rich in information as
hydrobiid viscera fixes well and head-foot features relax in a
near life-like state.
Inorganic shell material was removed by soaking specimens
in Bouin's Solution or hydrochloric acid. Animals were
dissected in dilute Bouin's Solution. Specimens were first
examined entire, after which the visceral coil was separated
from the proximal portion of the animal by tearing between the
anterior edge of style sac and kidney/pericardium. The pallial
roof then was torn from the head-foot, flattened out, and
pinned. The female glandular oviduct and associated structures
were examined from the left side. In cases where alcohol
material was not available, study was of dried animals
resuscitated by soaking in Bouin's Solution. Anatomical
illustrations were prepared from camera lucida drawings of
pinned out specimens.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
Three or four specimens of each sex (topotypes, when
available) were usually dissected for each species, although
additional series were added when species were widely
distributed or geographically variable in shell features.
Shell, opercula, and radulae were cleansed in commercial
bleach (CLOROX), rinsed in water, and then studied and
photographed using a Hitachi S-570 Scanning Electron
Microscope (SEM). With the exception of a few species, study
of radula was limited to the central radular teeth owing to the
perceived lack of variation in lateral and marginal teeth.
Animals were dried using a Denton DCP-1 Critical Point Drier
and studied with SEM to ascertain ciliation patterns on dorsal
cephalic tentacles and penis. Whole mounts of penes were
prepared by staining in hematoxylin followed by dehydration,
clearing, and mounting in balsam.
The following morphologic features were routinely scrutinized
while preparing species descriptions:
1. Shell: size, shape, thickness, number of whorls; protoconch,
teleoconch sculpture; whorl convexity; adapical shoulder
of whorls; aperture size, shape; thickness of inner shell lip,
relationship between lip and body whorl; inclination of outer
lip relative to coiling axis; umbilical development; periostracal
thickness, color.
2. Operculum: shape, thickness, color, number of whorls,
location of nucleus, frilling of whorl outlines on dorsal surface,
thickening of (ventral) attachment scar margin, development of
attachment region callus.
3. Digestive system: indentation of dorsal edge of central
radular tooth; number of lateral cusps; size (relative to lateral
cusps), shape of central cusp; number, size, shape, position of
basal cusp(s); robustness of dorsal support of basal cusps; depth
of basal sockets; width of basal process; thickness of lateral
angles; prominence of neck along outer edge of lateral angles;
size, shape of posterior caecum of stomach.
4. Animal pigmentation: color, intensity, pattern of pigment
on cephalic tentacles, snout, neck, foot, opercular lobe,
pallial roof, visceral coil.
5. Pallial cavity: length of ctenidium (relative to pallia!
cavity); height, width, number of ctenidial filaments; size,
position of osphradium (relative to ctenidial axis); bulge of
kidney into pallial cavity (relative to total length of kidney);
nature of kidney opening to pallial cavity.
6. Male animal: total whorls; testis whorls, position; size,
shape, thickness of prostate gland; extent of pallial portion of
prostate gland; coiling of vas deferens in pallial roof; size,
shape of penis, penial filament, distal lobe; orientation of lobe,
filament; number, size, position, orientation, fusion of penial
glands; pigmentation of penial filament.
7. Female animal: total whorls; ovary whorls, position;
extent of pallial portion of albumen gland (relative to total
length of gland); relative lengths of albumen, capsule glands;
number of distinct capsule gland regions; size, shape, position
of capsule gland opening; development of vestibule extending
anteriorly from capsule gland opening along pallial roof;