The most frequent feeders on Thalassia are the boring bivalves: Xylophaga or closely related gen: a. In addition to the eleven living specimens and the large number of dead shells recovered from burrows, a great many empty burrows in rhizomes, particularly from St. P120(off Georgia) and St. P 444(north of Cuba), bore witness to heavy attacks(Fig. Se-j). These are the first records of Thalassia being utilized by Xylophagainae.