ON THE BIOLOGY OF THE MESOGASTROPOD TRICHOTROPIS CANCELLATA HINDS, A BENTHIC INDICATOR SPECIES C. M. YONGE Department of Zoology, University of Glasgoiv, Glasgow, W. 2, Scotland, and the Friday Harbor Laboratories, University of Washington, Seattle 5, Washington The observations on the mesogastropod, Trichotropis cancellata Hinds, with which the paper is concerned, were made during a period of some ten weeks in the summer of 1959 spent at the Friday Harbor Laboratory of the University of Washington, Seattle. They were supplemented by examination of further samples of living animals later that year in Seattle and during the early months of 1960 when working at the Hopkins Marine Station, Pacific Grove. This research was not premeditated. It arose out of interest in an animal never previously encountered by the author. Thus, while a variety of most inter-esting points regarding ciliary feeding, protandric hermaphroditism, adaptation to a restricted range of bottom conditions and the mode of evolution of mesogastropod limpets were disclosed, no attempt could be made to probe deeper than was pos-sible by examination of the living animal, although a few points have been con-firmed and conclusions strengthened by subsequent sectioning of fixed material. But it is hoped that this general study may stimulate more detailed work. Par-ticularly desirable would be a histological and experimental study of the protandric reproductive system over the two-year life span postulated in this paper. More precise information, to be obtained by means of grab samples, about the precise distribution of this species in relation to bottom substrates could also be most in-forming. It is a pleasure to record thanks to colleagues of the summer season of 1959 at Friday Harbor, especially to Dr. Dixy Lee Ray and to Dr. R. L. Fernald who also sent additional samples of Trichotropis to Pacific Grove during February and March, 1960. Mr. Jefferson Conor kindly reported on animals left in aquarium tanks at Friday Harbor and sent samples of these animals. Dr. J. Connell and Mr. G. Bakus identified species of barnacles and sponges which live on the shells of Trichotropis. At Pacific Grove every facility needed was supplied by the Director, Dr. L. R. Blinks, and members of his staff. The figures which illustrate this paper have been prepared by the author's research assistant. Miss J. I. Campbell. Grateful acknowledgment is also made to the L'nited States Educa-tional Commission in the United Kingdom for award of a Fulbright Travel Grant and to the Carnegie Trust for the Universities of Scotland for a grant towards expenses while working at Pacific Grove. SYSTEMATIC POSITION The genus Trichotropis Broderip and Sowerby 1829 is one of 10 genera in the Family Trichotropidae which, with the Capulidae and the Calyptraeidae, con-160
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