Published online by Cambridge University Press: 15 September 2014
I have previously (Graham, 1934) noted the fact that in the bivalve mollusc Solecurtus scopula the structure of the outer gills is peculiar in that they possess no groove along the free edge as do the inner and the great majority of lamellibranch gills. In Solecurtus (fig. 1) the gills are rather long and narrow, the outer shorter than the inner on each side, leaving a small triangular area of the latter exposed at the anterior end as well as a narrow strip along the ventral margin. The outer gill is provided with a supra-axial extension reaching to the dorsal part of the body on each side. The lamellæ are plicate, and the filaments lying on the summits of the folds on the outer gill project at the free edge further than do those at the bottom of the folds, so that the entire gill has a wavy or scalloped edge. It was of interest to investigate the effect of this departure from the normal structure of the gill on the ciliary mechanisms found there.