On the anatomy of the pedunculate barnacle Lithotrya.

The genus Lithotrya G. B. Sowerby, 1822, comprises a group of pedunculate barnacles that have developed a rock- or shell-boring habit. Darwin dealt at considerable length with the genus in his Ray Society monograph in 1851, and since then only one new species has been described—L. pacifica Borradaile, 1900. In 1926, however, Seymour Sewell showed that, apart from one doubtful species, L. rhodiopus (Gray), all the others could be divided into two groups. One group of five, he suggested, constituted, in fact, a single species, L. dorsalis (Ellis). The other group of two I dealt with systematically in my report on the Great Barrier Reef Expedition collection (Cannon 1935) and came to the conclusion that they also represented a single species, L. valentiana (Gray). The material on which this paper is based consists mainly of a few specimens of L. valentiana, collected and fixed in Bouin, which were very kindly given to me by Professor C. M. Yonge. I have also to thank Dr L. A. Borradaile for specimens of L. dorsalis collected by him in the Maldive Islands in 1900, and the Discovery Committee for specimens of various barnacles which I have used for comparison. In addition, I still have the official collection of the Great Barrier Reef Expedition, and a few of these have now been sectioned. I have been careful, however, not to section critical specimens of my detailed list (Cannon !935, p. 5, table 1).