THE AMERICAN MIDLAND NATURALIST 47 
diaphragm incompletely formed; supra-anal absent, branchial and anal 
- openings suppressed with no tendency to a siphonal form; all four gills 
; both respiratory and marsupial; post-ventral margin of mantle undiffer- 
entiated; glochida semi-circular, ventral margin with irregular dentations; 
tachytictic, or short period (‘‘Summer’’) breeders. 
FAMILY I. MarGariTANIDAE Ortmann. 
a.—Gill septa oblique from base of gills, more vertically arranged and 
Shortens Vietha@s. Acc. sn. cess ...Genus I. CUMBERLANDIA, Ortmann 
1.—C. monodonta (Say)—(l. c). 
B.—Gills always with water-tubes, septa complete and parallel 
with gill filaments; gill-diaphragm complete; branchial and 
anal openings usually tend toward a siphonal form; all four 
sills or only outer, or parts of outer, marsupial; glochida 
generally suboval, spadiform, celtiform, spined or spine- 
JSST Rees 2 (EPA tunes Ae a FAMILY II. Unronrpag, Swainson 
(A).—Connection between anal and supra-anal openings short 
or absent; inner laminae of inner gills free from visceral 
mass; post-ventral margin of mantle not specialized; mar- 
supial undifferentiated, not distended when gravid; glochidia 
suboval, spineless, tachytictic for the most part.......... 
Sub-Family (1), UNIoNINAE, Ortmann 
a.—All four gills marsupial. 
(a)—Conglutinates club-shaped, pinkish, solid; beak sculpture 
concentric and slightly nodulated at base of post-umbonal 
ridge; disk unsculptured....Genus II. Fusconara Simpson 
2. F. undata (Barnes)—(1. b) 
(1). F. undata trigona (ea)—(t1. c) 
(2). F. undata trigonoides Frierson—(1. a) 
Sue paver Rak, )——(3.c) 
4. F. hebetata (Contad)—(t. c) 
5. F. ebena (Lea)—(t1. b) 
(b)—Conglutinates leaf-like, compressed, subsolid white; beak 
sculpture concentric, extending zigzag out on disk which is greatly 
Seth tiIred hy ach at soe «, che Aig HABE EU! Genus III AmBriEMa (Raf.) 
6. A. peruviana (Lamarck)—(tr. c) 
7. A. rariplicata (Deshayes)—(1. a) 
8. A. perplicata (Conrad)—(3. c) 
(3). A. perplicata Quintardi (Cragin)—(1. c) 
y 9. A. (plicata) costata (Raf.)—(1. a) 
Genus IV. MacGnonaras Utterback. 
10. WM. heros (Say)—(1. a) 
Genus V. QUADRULA (Raf.) 
11. Q. pustulosa (1ea)—(1. b) 
(4). Q. pustulosa schoolcraftensis (Lea)—(1. a) 
(5). Q. pustulosa asperata (1,ea)—(1. c) 
12. Q. quadrula (Raf.)—(1. b) 
(6). Q. quadrula contraryensis Utterback—(1. a) 
