BULLETIN FLORIDA STATE MUSEUM


erally perforate umbilicus, and a small, protruding apical whorl. Among the
eastern North American genera with a lobed verge it overlaps in shell mor-
phology with Cincinnatia and the eastern species placed in Pyrgulopsis.
Species of Cincinnatia are usually more obese, and the eastern species of Pyr-
gulopsis (letsoni, wabashensis, ozarkensis, and scalariformis) are narrower
than most Marstonia.
 Marstonia consists of two species lineages. One lineage, found in the Ten-
nessee River system and northward, has a large, squarish apical lobe and a
relatively small, slender penis. The second lineage, found in coastal drainages
of Georgia, has a more elongate apical lobe and a relatively robust penis.

 SPECIES OF QUESTIONABLE STATUS

 One lot, consisting of two specimens (UMMZ 161894), comes from the
Coosa River, Etowah Co., Alabama. The shell is conical-ovate in shape, has a
narrow umbilicus, and a constricted aperture. These specimens represent an
undescribed species that almost certainly is a Marstonia. It receives no further
discussion because of the scant material available.
 Four species currently placed in Pyrgulopsis may actually belong in Mar-
stonia: P. letsoni (Walker), P. wabashensis Hinkley, P. ozarkensis Hinkley, and
P. scalariformis (Wolf). These are small narrow hydrobiids that have in com-
mon a carinate body whorl. The verge of P. letsoni is similar to that of Mar-
stonia, except that it is longer, more slender, and has a small papilliform api-
cal lobe (Berry 1943:43). The anatomy of the type species of Pyrgulopsis, P.
nevadensis (Stearns), is not known. Thus the relationship of Pyrgulopsis to
other genera remains undetermined, and the relationships of the eastern spe-
cies to P. nevadensis need to be corroborated. The generic allocations of the
eastern species placed in Pyrgulopsis require further anatomical studies.

 KEY TO THE SPECIES OF Marstonia
1. Verge with an elongate apical lobe; penis large and robust (Fig. 19, A-B). Shell
 minute, less than 2.7 mm long at maturity with four or more whorls ... ............... .. 2
la. Verge with a squarish apical lobe; penis short and slender (Fig. 11, A-B). Shell
 larger, 3.5 mm long at maturity with 4.5 or more whorls.. ........ ......................... 4
2. Shell thin, fragile, transparent, conical, with an incomplete peristome across the
 parietal margin; verge with a single gland on apical lobe. Ocmulgee River Sys-
 tem ................................................................................................... agarhecta T hom pson
2a. Shell thick, solid, nearly opaque, ovate-conical; with a complete peristome across
 parietal margin; verge with two glands, one on the apical lobe and one near the
 base of th e verge ......................................... ............ ... ....... ... .............. ... .. 3
3. Umbilicus wide; shell broadly ovate, 0.70-0.80 times as wide as high; whorls
 strongly shouldered, flattened at periphery; suture descending in lateral profile.
 O geechee River System ................... ................... ........ ........................... halcyon n. sp.
3a. Umbilicus narrow; shell ovate-conical, 0.66-0.73 times as wide as high; whorls
 rounded, not strongly shouldered; suture not descending to the aperture in lateral
 profile. Flint River System ...... ... ...................... .... ................. castor n. sp.
4. Shell thick, solid, nearly opaque; umbilicus closed or narrowly rimate...................... 5


Vol. 21, No. 3