Depressed, the summit hardly marked, and much more narrow in front than behind; exterior brownish, interior light blue. _P. scutellaris._ The buckler Patella. Pl. 2, fig. 5. Depressed, summit sub-anterior, radiated from the summit to the margin; brown colour, with a yellowish band parallel to the margin. _P. pectinata._ The pectinated Patella. Pl. 2, fig. 6. Oval, summit well marked and anteriorly inclined; ribbed from the summit to the margin, which is slightly convex in the middle. _P. cymbularia._ The cymbular Patella. Pl. 2, fig. 7. Oval, thin, pearly, with a festooned margin; summit nearly marginal; colour white, shaded with very light brown. FAMILY III. CALYPTRACEA. Seven genera. The genera that constitute this family were separated by Lamarck from the Patella of Linnæus. 1. Parmaphora. The Duck’s-bill Limpet. Three species. The characteristic distinctions of this shell were first pointed out by De Blainville. Shell elongated, very depressed; the summit greatly post-medial, and evidently inclined behind; aperture as large as the shell; the lateral edges straight and parallel, the posterior rounded, the anterior sharp and notched in the middle; muscular impression large, elongated oval, slightly open in front. Parmophora Australis. P. brevicula. P. granulata. _P. Australis._ The Australian Parmophorus. Shell oblong, depressed; vertex slightly recurved; striated concentrically; one margin rounded, and the other truncated. 2. Emarginula. The Slit Limpet. Four species. Most of the shells of this genus are small; some are elevated, and others of a widely-depressed conical form. Shell conical, recurved; summit entire; slit, or more or less hollowed on the anterior side; a muscular impression in form of a horseshoe, open behind and thicker at the beginning. Emarginula Blainvillii. E. marginata. E. fissura. E. rubra. _E. Blainvillii._ Blainville’s Emarginula. Shell with the notch or slit in the middle of the back, and not extending to the margin. _E. fissura._ The slit Emarginula. Pl. 32, fig. 5. Oval, compressed, summit well marked, with reticulated striæ and ribs; fissure extending half way from the margin to the summit; exterior light brown, interior white. _E. marginata._ The marginated Emarginula. More compressed than the preceding; summit distinct, anterior margin formed like a gutter. 3. Fissurella. The Keyhole Limpet. Nineteen species. The perforation not being perfectly round, but generally ovate oblong, procured for this genus its common name, by which it is easily distinguished.