23 
d. Siphons separate. Shell attached by one valve. Clavicle large, 
sub cylindrical. 
8. Chamostrea. 
1. C. albida. 
v. Hinge toothed or toothless. Cartilage external, marginal. Shell 
pearly. Periostraca hard, polished. 
Fam. 1 7. Muteladce. 
Foot large, compressed, angular in front. Pedal opening very 
large. Gills large. Lips very large, semioral, attached by the 
straight line without the free point existing in Unio and Anodon. 
Shell scarcely to be distinguished from Unio or Anodon, but the 
hinder submarginal scar is rather more truncate. 
1. Mutela. 
1. M. nilotica, t. 361. f. 2. 
2. M. rubens, t. 328. f. 1. 
2. Castalia. 
1. C. ambigua, t. 361. f. 3. 
3. Hyria. 
1. H. Syrmatophora, t. 328. f. 2. 
II. Foot conical, acute, angularly bent behind for leaping. 
Fam. 18. Cardiadce. 
Gills narrow, elongate, floating, only attached at the upper end, 
united together behind the foot. Shell equivalve. Cardinal teeth 
conical, forming a cross when the valves are closed. Cartilage ex- 
ternal, marginal. 
a. Shell gaping, and furnished with a serrated hinder margin. 
1. Cardium. 
1. C. hians, t. 330. f. 1. 
2. Bucardium. 
1. B. ringens?, t. 330. f. 5. 
b. Shell closed, and smooth or nearly smooth behind. 
3. Cerastes. 
1. C. edule, t. 329. f. 5, t. 330. f. 2, 6, t. 331. f. 1, 2. 
2. C. echinatura, t. 330. f. 1. 
3. C. rusticum, t. 330. f. 8. 
4. C. , t. 330. f. 3. 
5. C. aculeatum?, t. 329. f. 1. 
6. C. pygmseum, t. 330. f. /• 
7. C. fasciatum, t. 330. f. 4. 
8. C. , t. 330. f. 10. 
9. C. norvegicum, t 329. f. 4. 
