* Mr. Grant Allen's theory set out in his “Science in Arcady” explains these curious spiral projections as follows :—“That well-known frequenter of Australian harbours, the Port Jackson shark lays a pear-shaped egg, with a sort of spiral staircase of leathery ridges winding round it outside, Chinese-pagoda wise, so that even if you bite it (I speak in the person of the predaceous fish) it eludes your teeth and goes dodging off screw-fashion, into the water beyond.”

Mr. E. R. Waite in vol. xxv. of the Linnean Society's Journal, says, on the contrary, “the elastic flanges permit the egg to be forced further into a fissure, whence extraction is resisted by the free edges of the ribbon catching against the rock.”—(EDS.)