1. Ostrea 100 World-wide--in estuaries, attached.
2. Anomia 20 India, Australia, China, Ceylon--
attached to shells from low water
to 100 fathoms.
Placuna 4 Scinde, North Australia, China--in
brackish water.
3. Pecten 176 World-wide--from 3 to 40 fathoms.
Lima 20 Norway, Britain, India, Australia--
from 1 to 150 fathoms.
Spondylus 70 Tropical seas--attached to coral-reefs.
4. Avicula 25 Britain, Mediterranean, India--
25 fathoms.
Perna 18 In tropical seas--attached.
Pinna 30 United States, Britain, Mediterranean,
Australia, Pacific--low water to
60 fathoms.
5. Mytilus 70 World-wide--between high and low water
mark.
Modiola 70 British and tropical seas--low water
to 100 fathoms.
6. Arca 400 In warm seas--from low water to 200
fathoms.
Pectunculus 58 West Indies, Britain, New Zealand--
from 8 to 60 fathoms.
Nucula 70 Norway, Japan--from 5 to 100 fathoms.
7. Trigonia 3 Off the coast of Australia.
8. Unio 420 World-wide--in fresh waters.
Anodon 100 North America, Europe, Siberia--in
fresh waters.