"The Shark Bay Pearl Shell” Carcharius, the genus name of the formidable Nurse Sharks. Shell flat as in P. maxima (Silver-lip or Gold-lip, the large white Mother-of-Pearl shell of North Australia, Papua, and Malaya), but differing in the relatively greater size of the rostrum and the more vertical posterior margin of the nacre. Anterior teeth very abortive; lateral teeth, a tiny lamina or elongated facet just posterior to the ligament; posterior angle of the nacre, where its margin meets the hinge line, is a right angle; no marked sinus in the hinder margin, but a slight notch; hinge nearly as long as the antero-posterior measurement of the nacre; lappet-like lip processes crimped: shell colour pale-greyish or greenish-yellow, almost white, with traces of four or five green radial bands, which are never very distinct; inside of margin pale yellow, sometimes with brown markings; nacre, distinct yellowish-green. A South Australian small specimen figured has length 117 mm., height 117 mm., section 20 mm. Type locality: Shark Bay, Western Australia, where it was taken in quantities for the London market, and realised from 10s. to 20s. per cwt., chiefly for the manufacture of small buttons. Yields pearls, mostly of inferior quality. Loc.: Subfossil only in South Australia, common at Murat Bay, and seems to postulate a warmer climate. N.W.A., S.W.A., S.A. (sub-fossil). A related Tertiary species is Pinctada crassicardia Tate 1886.