29 
4. Subgenus Margaritana, 
Having one tooth (cardinal). 
5. Subgenus Plagiodon, 
Having a double transverse cardinal tooth. 
6. Subgenus Monocondylaea, 
Having a simple callus. 
7. Subgenus Dipsas, 
Having a linear tooth under the dorsal 
margin. 
8. Subgenus Anodonta, 
Having no teeth. 
9. Subgenus Columba, 
Without teeth, but having an inflected 
palleal cicatrix. 
10. Subgenus Byssanodonta, 
Having no teeth, but is always attached 
by a byssus. 
1. Subgenus Iridina, 
Having a granulate dorsal margin, and 
furnished with two siphons. 
2. Subgenus Spatha, 
Having a dorsal margin non-crenulate, 
and furnished with two siphons. 
3. Subgenus Mycetopus, 
Having a straight, smooth, dorsal margin, 
an furnished with a long extensile foot. 
Î Symphinote — Alas, comp ana ta 
Barn. 
Non-Symphinote — Al. undulata 
Say. 
I Non-Symphinote — Plag, isocar- 
I dioides Lea. 
I Non-Symphinote — Mono, para- 
\ g u ay an a D’Orb. 
I Symphinote — Dipsas plicatus 
( Leach. 
• Symphinote — An. magnifica 
Lea. 
Non-Symphinote — An. fluviatilis 
Dill. 
J Non-Symphinote — ColumbaBlain- 
j villi an a Lea. 
! Non-Symphinote — By ssan odonta 
Par an en sis 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: — 
1. Plicate (Unio plicatus Lesueur). 4. Sulcate (Unio Kraussii Lea). 
2. Nodulous (Unio pustulosus Lea). 5. Smooth (Unio complanatus Solan). 
3. Spinous (Unio spinosus Lea). 
Euch of these subdivisions group according to the form of their outline, thus : — 
1. Quadrate (Unio asperrimus Lea). 3. Oblique (Unio clavus Lam.). 
2. Triangular (Unio triangularis Barnes). 4. Oval (Unio ligamentinus Lam.) 
