114 BULLETIN FLORIDA STATE MUSEUM Vol. 21, No. 3

 TABLE OF CONTENTS

IN T R O D U C T IO N .................................................................................................. .......................... 1 14
A C KN O W LE D G M E N T S .... ........................................................................................................ ...... 115
M arstonia F C BAKER 1926 ............................ ................................................ ...... ... 115
SPECIES OF Q UESTIONABLE STATUS .............................................................................................. 118
K EY TO THE SPECIES OF M arstonia .............................................................................................. 118
M arstonia arga new species ................................................. ............................................... 119
M arstonia ogm orhapha new species ......................................... ......................................... 120
M arstonia pachyta new species .............................................. ............................................ 121
M arstonia olivacea (P ILSBRY) ............................... ....................................................................... 122
M arstonia lustrica (P ILSBRY .......................................................................................................... 124
M arstonia halcyon new species ........................................................ ........................................ 128
M arstonia castor new species............................... ..................................................................... 130
M arstonia agarhecta T HOM PSON .................................................................................................. 130
L IT E RA T U R E C IT E D ................................................... ......................... .......................................... 13 1
F IG U R E S .......................................................................................................................................... 1 3 3



 INTRODUCTION

 Attempts to define many genera and species of southeastern hydrobiid
snails necessitates restudy of taxa long known from the north-central United
States. A genus of particular note is Marstonia and its wide-ranging cold-
temperate species M. lustrica (Pilsbry). Even though the species is widely dis-
tributed throughout the Great Lakes region and has been known since 1890,
there exists a dearth of information on its eco-geographic variation and
anatomy. All previous studies on geographic variation were confined to single
states, and anatomical observations have been limited to the verge of the male.
The discovery of several undescribed species of Marstonia in the Tennessee,
Flint, Ocmulgee, and Ogeechee river systems necessitates a review of all other
known taxa referable to the genus. Anatomical data provide a basis for re-
lating Marstonia to other North American genera with a lobed verge, and to
similar European genera about which a great deal of anatomical information
is available, particularly through the studies of P. Radoman and H. D. Boeters
(see references). The following study does not pretend to be definitive. Some
species from the Tennessee and Coosa rivers are left undescribed because
anatomical specimens of these forms are not available. Also, additional spe-
cies can be anticipated in other river systems.
 Marstonia was regarded as a subgenus of Amnicola until recently (Taylor
1960:51), as were other distinct groups of hydrobiid snails that possess small,
simple, conical shells. All specific and subspecific forms of Marstonia de-
scribed prior to 1969 were named as species of Amnicola. Morrison (1949:13-
15) demonstrated that Amnicola and Marstonia belong to different subfamilies
(see Thompson 1968:147-167). Marstonia currently is placed in the subfamily
Nymphophilinae Taylor 1966.