This genus will attract attention, although it cannot be gathered. It is a thin, brittle, scaly substance of indefinite form, which expands horizontally and resembles a lichen. It forms brown and pink crusts on other algæ and on rocks, stones, and shells. ORDER =BANGIACEÆ= GENUS ^Bangia^ ^B. fusco-purpurea^ ("brown-purple"). Fine, hair-like, unbranched, dark-purple filaments, one inch to six inches long. It grows in large patches on rocks and woodwork, floating free, but falling into soft, silky, fleece-like masses when left by the tide. Common on northern shores. (Plate XXXVII.) GENUS ^Porphyra^ ("/Purple dye/") This plant, except in color, is like the green alga /Ulva/. In color it is purple of various shades. The species are named from variations in the outline of the frond. They are found everywhere, and throughout the year. The plants are edible, being the laver of commerce, eaten principally by the Chinese, who make them into soup. ^P. vulgaris.^ Frond a broad, thin membrane of purple color, three to twelve inches across; margin much waved; sometimes attached at the center, often widely expanded and folded, sometimes deeply lobed. (Plate XXXVII.) ^P. laciniata.^ Differs from /P. vulgaris/ in being divided into narrow segments or into wavy, ribbon-like forms. (Plate XXXVII.) [Illustration: PLATE XXXVII. Corallina officinalis. Bangia fusco-purpurea. Porphyra vulgaris. Porphyra laciniata.] PART II MARINE INVERTEBRATES I PORIFERA (SPONGES) TABLE SHOWING THE CLASSIFICATION OF THE SPONGES DESCRIBED IN THIS CHAPTER Phylum and Class =PORIFERA= Subclass =Calcarea= Order =HETEROCŒLA= Family ~SYCONIDÆ~ Genera Species ^Grantia^ ^G. ciliata^ ^Leucosolenia^ ^L. botryoides^ Subclass =Non-Calcarea= Order =CHONDROSPONGIÆ= Family ~SUBERITIDÆ~ ^Suberites^ ^S. compacta^ ^Polymastia^ ^P. robusta^ ^Cliona^ ^C. sulphurea^ Order =CORNACUSPONGIÆ= Family ~DESMACIDONIDÆ~ ^Esperiopsis^ ^E. quatsinoensis^ ^Microciona^ ^M. prolifera^ Family ~HETERORRHAPHIDÆ~ ^Tedania^ Family ~HOMORRHAPHIDÆ~ Genera Species ^Halichondria^ ^H. panicea^ Family ~SPONGIDÆ~ Subfamily ~EUSPONGINÆ~