NAIADKS OF. MISSOURI 7 



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 



shorter ventrad Genus I. Cumberlandia, Ortmann 



I. — C. monodonta (Say) — (1. 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 

 gills or only outer, or parts of outer, marsupial; glochida 

 generally suboval, spadiform, (jeltiform, spined or spine- 

 less FAMILY II. Unionidae, 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 undifTerentiated, not distended when gravid; glochidia 



suboval, spineless, tachytictic for the most part 



Sub-Family (I), 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. Fusconaia Simpson 



2. F. undata (Barnes) — (i. b) 



(i). F. undata trigona (Lea) — (i. c) 



(2). F. undata trigonoides Frierson — (i. a) 



3. F. flava (Raf.) — (j.c) 



4. F. hebetata (Conrad) — (i. c) 



5. F. ebena (Lea) — (i. b) 



(b) — Conglutinates leaf-like, compressed, subsolid white; beak 

 sculpture concentric, extending zigzag out on disk which is greatly 

 sculptured Genus III Amblema (Raf.) 



6. A. peruviana (Lamarck) — (i. c) 



7. A. rariplicata (Deshayes) — (i. a) 



8. A. perplicata (Conrad) — (3. c) 



'(3). A. perplicata Quintardi (Cragin) — (i. c) 



9. A. (plicata) costata (Raf.) — (i. a) 

 Genus IV. Magnonaias Utterback. 



10. M. heros (Say) — (i. a) 

 Genus V. Quadrula (Raf.) 



11. Q. pustulosa (Lea) — (i. b) 



(4). Q. pustulosa Schoolcraftensis (Lea) — (i. a) 

 (5). Q. pustulosa asperata (Lea) — (i. c) 



12. Q. quadrula (Raf.) — (i. b) 



(6). Q. quadrula contraryensis Utterback — (i. a) 



