48 NAIADES OF MISSOURI 
13. Q. nodulata (Raf.)—(1. b) 
14. Q. fragosa (Contrad)—(t1. b) 
15. Q. aspera (Lea)—(1. c) 
16. Q. nobilis (Conrad)—(2. a) 
17. Q. verrucosa (Raf.)—(1. c) 
18. Q. metanevra (Raf.)—(1. c) 
(7). Q. metanevra Wardu (Lea)—(1. b) 
19. (Q. cylindrica (Say)—(3. c) 
b.—Only outer gills marsupial. 
(a)—Supra-anal opening absent; beak sculpture zigzag; disk greatly 
Sleyolll ong obeelo am Get CEs a Sunes, crete Genus VI. RotTunpDartia (Raf.) 
20. R. tuberculata (Raf.)—(1. c) 
21. R. granifera(Lea)—(1. b) 
(b)—Supra-anal present but short; beak sculpture concentric but 
disappearing toward disk which is mostly unsculptured. 
Genus VII. PLETHOBASUS (Simpson) 
22. P. cooperianus (Lea)—(2. c) ‘ 
22.) PB. aesopus (Green)—-(n,b) 
Genus VIII. PLeuROBEMA (Raf.) 
24. P. obliquum (lamarck)—(1. b) 
(8). P. obliquum plenum (Lea)—(3. c) 
(9). P. ebliquum pyramidatum (Lea)—(1. c) 
(10). P. obliquum catillus (Conrad)—(t. c) 
(11). P. obliquum coccineum (Conrad)—(t. c) 
25. PP. catillus (Conrad)—(3. c) 
26. P. coccineum (Conrad)—(3. c) 
27. P. missourense (Marsh)—(3. c) 
28. P. Utterbackit Frierson—(3. c) 
Genus IX. Ev.iprtio (Raf.) 
29. E. nigra (Raf.)—(2. c) 
30. E. dilatata (Raf.)—(2. a) 
(12). EF. dilatata subgibbosa (Lea)—(3.c) 
(13). £. dilatata delicata (Simpson)—(3. c) 
Genus X. UNIONERUS (Conrad) 
31. U. tetralasma (Say)—(1..a) 
(14). U. tetralasma comptodon (Say)—(1. a) 
(B).—Mantle connection between anal and supra-anal openings always 
present, very long and moderate; inner laminae of inner gills usually 
free from the visceral mass; marsupia occupying entire outer gills | 
only, distended ventrad and with lateral water-tubes when gravid; 
post ventral margin of mantle not differentiated; glochidia subtrian- 
gular, or spadiform, spined; bradytictic or long period (‘‘ Winter’’) 
ta hole{G Cl a eens Me SPL S Nas Tia Rat Sub-Family II. ANODONTINAE Ortmann 
a.—Inner laminae of inner gills free from visceral mass; beak sculpture 
coarse, double-looped. 
(a)—Mantle connection between anal and supra-anal openings 
moderately long; hinge rather complete, shell sculptured and 
somewhaty thick). asc. k memes Genus XI. Sympnynota (Lea) 
