Among a number of Cirripede plates from the Chalk Marl and Cambridge Greensand of Cambridge submitted to me some time ago, were certain fossils which at first puzzled me considerably. Although there were more than twenty examples, all came apparently from the same side of the animal, that is, they were not left and right, and this led me to suspect that they were not Cirripede valves, and to examine them more closely. One edge close to the narrow end of the shell was then seen to be broken quite clean and straight, and on comparing these fossils with some Pelecypod shells from the same horizon it was quite clear that they were the anterior ears of right valves of Aucellina gryphœides (Sow.) (Text-fig. 7, p. 170), a shell belonging to the family Pteriidae (see H. Woods, Pal. Soc. Monogr. Cretaceous Mollusca, 1905, vol. ii, p. 72, pi. x, figs. 6–13). Other specimens submitted at various times from Jurassic and Cretaceous rocks, turned out on examination to be the anterior ears of the right valves of Pelecypod shells like Pecten, and a number of such specimens were included among some Cirripede plates from the Chalk of liugen obtained for the British Museum by Frau Agnes Laur.