BULLETIN FLORIDA STATE MUSEUM


 DISTRIBUTION (FIG. 8).-Marstonia arga is known only from the Tennessee River in the vicinity
of the Guntersville Reservoir in northeastern Alabama and from Shoal Creek. Although numer-
ous collections of mollusks were made in creeks, rivers, and springs draining into the Tennessee
River between Florence, Alabama, and Chattanooga, Tennessee, this snail was not encountered
except at the above stations.
 TYPE LOCALITY.-Guntersville Reservoir, at mouth of Mink Creek, 9.8 mi. SW Scotsboro,
Jackson Co., Alabama. HOLOTYPE: UF 22286, collected 14 September 1973 by Fred G. Thomp-
son. PARATYPES: UF 22287 ( 800), same data as holotype.
 SPECIMENS ExAMINED.-TENNESSEE RIVER: ALABAMA. Jackson Co.: Guntersville Reser-
voir, 4.8 mi. SE Scotsboro (UF 22299); 4.3 mi. ESE Scotsboro (UF 22298); 5.1 mi. ESE Scotsboro
(UF 22300); 11.2 mi. SW Scotsboro (UF 22302); mouth of North Sauty Creek, 7.5 mi. SW Scots-
boro (UF 22289); near mouth of Sauty Creek, 8.1 mi. SW Scotsboro (UF 22301); 3.3 mi. SE Holly-
wood (UF 22297). Marshall Co.: Guntersville Reservoir, Honeycomb Creek boat landing, 4.2 mi.
WSW Henryville (UF 22291); south shore of bay S of Honeycomb Creek (UF 22293); small bay
2.1 mi. SW Henryville (UF 22292); Creek Reservation, between Tennessee River miles 356 and
357 (UF 22295); Mill Creek Bay, 5.5 mi. NE Guntersville (UF 22303); Town Creek Bay, 8.8 mi.
NE Guntersville (UF 22288); Street Bluff Bay, 4 mi. WNW Guntersville (UF 22294); Street Bluff
Bay, 3.1 mi. W Guntersville (UF 22290). SHOAL CREEK: ALABAMA. Lauderdale Co.: Shoal
Creek at Lauderdale Co. Hwy. 8 (UF 22306, UF 22308). TENNESSEE. Lawrence Co.: Shoal
Creek, 0.3 mi. NE Iron City (UF 22307).
 REMARKS.-This species appears to be favored by the creation of large
quiet bodies of water due to damming of the Tennessee River. It has not yet
been found at lentic stations in the Tennessee River below the Guntersville
Dam, although it undoubtedly occurs there. In Shoal Creek it was collected
in quiet pools of water.
 This snail was found most abundantly in beds of Najas in quiet, shallow
water but generally not on other plants. Three genera of aquatic angiosperms
form extensive colonies within the Guntersville Reservoir; Elodea, Myrio-
phyllum, and Najas. Extensive search was made in beds of all three genera,
and only rarely was Marstonia arga found on Myriophyllum. It was never en-
countered on Elodea. Occasional specimens were found on algae-coated
cobbles in water less than two feet deep and in piles of submerged dead tree
leaves.
 ETYMOLOGY.-The species name arga is derived from the Greek argos,
meaning white, and refers to the white aperture caused by the thick internal
callus and shell wall.


 Marstonia ogmorphaphe new species
 DIAGNOSIs.-The verge of this species is most similar morphologically to that of M. lustrica
and of species living in the Tennessee River System because of the enlarged, squarish apical lobe
on the verge and the short, terminal penis. It is more similar to other Marstonia from the Ten-
nessee River System than to M. lustrica in having an elongate reniform prostate. M. ogmorhaphe
is distinguished from all other species of Marstonia by (1) its large size (4-5 mm), (2) its large num-
ber of whorls (5.2-5.8), (3) its deeply incised suture producing strongly shouldered whorls that
are almost flat above, (4) its complete aperture that is broadly ovate in shape with a rounded pos-
terior corner, (5) its outer lip which is slightly arched forward in lateral profile, (6) its thin shell,
(7) its conical-terete shape, and (8) its enlarged bursa copulatrix with a completely exposed duct.
 SHELL (FIcs. IC, 9A-E).-The shell is conical-terete in shape. Young specimens are conical-
ovate. Subsequent growth of the last two whorls is progressively lower in position, producing a
terete shape. Large specimens with more than five whorls are about 1.67-1.82 times as long as


Vol. 21, No. 3