CLASS IV. — ACEPHALA. 
liii 
ORDER IX. — Cyclobranchiata. 
The gills, in the forms of leaflets, are situated under the edge of 
the mantle. In other respects the order is assimilated to the last. 
Genus. 
I. Patella, L. 
II. Chiton, L 
Example of Species. 
Patella, Gm. 
Chiton, L. 
CLASS IV. — ACEPHALA. 
In this class there is no apparent head, the principal ganglion of 
the brain being over the mouth, which is situated at the bottom, or 
between the folds of the mantle. 
ORDER I. — Acephala Testacea. 
In this order, the animals have four branchial leaflets. All the 
bivalves, and many multivalves, belong tp it. 
Family. Genus. Subgenus. Example of Species, 
s f 1. Radiolites, Lam. 
2. Spherulites,Larae^e- 
rie 
3. Calceolaria 
4. Hippurites 
5. Batolithes, Montf. 
1. Ostrea. prop. Brug., Os. edulis, L. 
2. Gryphsea, Lam Gr. tricarinata 
3. Pecten, Brug Os. maxima, L. 
4. Lima, Brug. Os. lima, L. 
5. Pedum, Brug Os. spondyloidea, Gm, 
III. Hinnita, Defr Hinnita gigantea, Gray 
IV . Plagiostoma, Sowerby PI. gigas, Sow. 
CV» Pachytes, Defr. Pac. spinosus, De F. 
I. Acarda, 
Ostracita,Z«. 
Peyrouse . 
II. Ostrea, Lin. 
