THe ciliary feeding currents and their associated organs of bivalve molluscs have been extensively studied both morphologically and experimentally (Ridewood, 1903; Wallengren, 1905 ; Kellogg, 1915 ; Yonge, 1923, 1926b, 1928 ; Atkins, 1936, 1937, 1937a, 1937b, 1938, 1938a; Purchon, 1941, 1955). Among the wood boring lamellibranchs, such a study has been carried out on Teredines like Teredo navalis (Sigerfoos, 1908) and Bankia indica (Nair, 1957). The gills in these forms are highly reduced and do not possess any ciliary mechanisms for sorting waterborne food items. Purchon (1941) has demonstrated a similar condition in the pholad Xylophaga dorsalis while he found five species of rock-boring pholads (Barnea parva, Pholadidea loscombiana, B. Candida, Pholas dactylus, Zirphaea crispatd) possessing well developed ctenidia and ciliary currents capable of sorting food material. Purchon infers that the well developed ctenidia with food sorting mechanisms are associated with their plankton feeding habit. The only other pholad known to be wood boring is Martesia sp. of which two are known to occur in Madras waters; M. striata and M. fragilis and these wood boring pholads appear to feed exclusively on plankton. It was felt that a detailed study of the ciliary sorting currents and the anatomical features of the mantle, the siphons and the ctenidia of M. fragilis will be of interest by itself and for comparison with other rock-boring pholads. 

cilliary, martesia fragilis