PROTOBRANCHS | |
| Protobranchs include early bivalves, which were shallow burrowers in soft substrata, plus living species such as Solemya sp. Protobranchs burrow with their anterior ends pointed downward and their posterior ends directed toward the surface. They are selective deposit feeders, consuming food particles picked up by the lips or with labial palps on either side of the mouth. |  |