On the Biology and Palaeontology of Some Predators of Bivalved Mollusca

A summary is given of the feeding habits of known predators on bivalve molluscs, including birds, fish, Pinnipedia, Mollusca, Arthropoda and Asterozoa. The fossil record of these groups, and of other possible extinct predators, is discussed in relation to the fossil record of the bivalves. It is concluded that asteroids are, and were, probably the most important of all predatory groups, and their ethology is presented in some detail. The relationship between the earliest Asterozoa and coextant Bivalvia in the Ordovician is discussed, and it is concluded that both intraoral and extraoral types of asteroid feeding were established at an early stage in the Palaeozoic. The known escape responses of Recent mollusca are described. It is postulated that several types of protective adaptation may have been important in the evolution of the Bivalvia: in particular, it is suggested that the primary significance of many types of radial ribbing lies not in the ribs themselves, but in the interlocking of the commissure that gave rise to them.