Valuable notices of Ceylon shells are to be found in detached papers, in periodicals, and in the scientific surveys of exploring voyages. The authentic facts embodied in the monographs of Reeve, Kuster, Sowerby, and Kienn, have greatly enlarged the knowledge of the marine testacea; and the land and fresh-water mollusca have been similarly illustrated by the contributions of Benson and Layard in the _Annals of Natural History_.
The dredge has been used but only in a few insulated spots along the coasts of Ceylon; European explorers have been rare; and the natives, anxious only to secure the showy and saleable shells of the sea, have neglected the less attractive ones of the land and the lakes. Hence Mr. Hanley finds it necessary to premise that the list appended, although the result of infinite labour and research, is less satisfactory than could have been wished. "It is offered," he says, "with diffidence, not pretending to the merit of completeness as a shell-fauna of the island, but rather as a form, which the zeal of other collectors may hereafter elaborate and fill up."
Looking at the little that has yet been done, compared with the vast and almost untried field which invites explorers, an assiduous collector may quadruple the species hitherto described. The minute shells especially may be said to be unknown; a vigilant examination of the corals and excrescences upon the spondyli and pearl-oysters would signally increase our knowledge of the Rissoæ, Chemnitziæ, and other perforating testacea, whilst the dredge from the deep water will astonish the amateur by the wholly new forms it can scarcely fail to display.
Dr. Kelaart, an indefatigable observer, has recently undertaken to investigate the Nudibranchiata, Inferobranchiata, and Tectibranchiata; and a recently-received report from him, in the Journal of the Ceylon Branch of the Royal Asiatic Society, in which he has described fifty-six species,--thirty-three belonging to the genus Doris alone--gives ample evidence of what may be expected from the researches of a naturalist of his acquirements and industry.
The arrangement here adopted is a modified Lamarckian one, very similar to that used by Reeve and Sowerby, and by MR. HANLEY, in his _Illustrated Catalogue of Recent Shells_.[1]