dae. 
et — ne, 
2. Genus Platicis. 
ioni 
Family Un 
1. Plicate (Unio plicatus Lesueur). 
2. Nodulous (Unio pustulosus Lea). 
1. Genus Margaron. 
4. 
5. 
6. 
-ı 
<o 
Subgenus Margaritana, 
Having one tooth (cardinal). 
Subgenus Plagiodon, 
Having a double nn cardinal tooth. 
Subgenus Monocondylaea, 
Having a simple callus. 
. Subgenus Dipsas, 
Having a linear tooth under the dorsal 
margin. 
. Subgenus Anodonta, 
Having no teeth. 
. Subgenus Columba, 
Without teeth, but hayınz an inflected 
palleal cicatrix. 
. Subgenus Byssanodonta, 
Having no teeth, but is always attached 
by a byssus. 
. Subgenus Iridina, 
Having a granulate dorsal margin, and 
furnished with two siphons. 
Subgenus Spatha, 
Having a dorsal margin non-crenulate, 
and furnished with two siphons. 
. Subgenus Mycetopus, 
Having a straight, smooth, dorsal margin, 
an furnished with-a long extensile foot. 
Symphinote — Alas. comp anata 
Barn. 
Non-Symphinote — Al. undulata 
Say. 
Non-Symphinote — Plag. isocar- 
dioides Lea. 
Non-Symphinote — Mono. para- 
guayana D’Ork. 
Leach. 
Symphintte — An. magnifica 
Lea. 
Non-Symphinote — An. fluviatilis 
Dill. 
Non-Symphinote—ColumbaBlain- 
j ranlipete — Dipsas plicatus 
villiana Lea. 
Non-Symphinote —Byssanodonta 
Paranensis D’Orb. 
Non-Symphinote — J. exotica Lam. 
| Non-Symphinote — J. rubens Desh. 
Non-Symphinote — Myc. soleni. 
formis D’Orb. 
After the divisions of Symphinote and Non-Symphinote shells, we have the five conditions 
in which the outward of the shell is found, viz: — 
3. Spinous (Unio spinosus Lea). 
Euch of these subdivisions group according to the form of their outline, thus: — 
Sn 
Quadrate (Unio asperrimus Lea). 
. Triangular (Unio triangularis Barnes). 4. Oval (Unio ligamentinus Lam.) 
4. Sulcate (Unio Kraussii Lea). 
5. Smooth (Unio complanatus Solan). 
3. Oblique (Unio clavu:s Lam.). 
