^P. Gouldii.^ Body cylindrical, a foot or more in length, a quarter or half of an inch in diameter when expanded; but the body constantly changes in size and shape as it is contracted or expanded; surface of body parchment-like in texture and marked off in small squares; color dull white to light brown. It is found on the New England coast in sand and gravel at low-water mark. IV MOLLUSCOIDA TABLE SHOWING THE CLASSIFICATION OF THE MOLLUSCOIDA DESCRIBED IN THIS CHAPTER Class =POLYZOA= Subclass =Ectoprocta= (/Excretory opening outside lophophore; mouth in center of circle of tentacles; tentacles retractile/) Order =GYMNOLÆMATA= (/Circular lophophore/) Suborder ~CYCLOSTOMATA~ (/Tubular calcareous zoœcia, with circular apertures devoid of closing apparatus/) Set ARTICULATA (/Erect branches divided at intervals by chitinous joints/) Genera Species ^Crisia^ ^C. eburnea^ Set INARTICULATA (/Erect or adherent zoarium; unjointed/) ^Tubulipora^ ^T. flabellaris^ ^Diastopora^ ^D. patina^ Suborder ~CHEILOSTOMATA~ (/Calcareous or chitinous zoœcia, usually with opercula; avicularia, vibracula, and ovicells often present/) Set CELLULARINA (/Flexible erect forms/) ^Ætea^ ^Æ. anguinea^ ^Eucratea^ ^E. chelata^ ^Cellularia^ ^C. ternata^ ^Caberea^ ^C. Ellisii^ ^Bugula^ ^B. turrita^ ^B. Murrayana^ ^B. flabellata^ Set FLUSTRINA (/Cells quadrate; front wall of zoœcium membranous or depressed, and has ridge-like margin/) ^Flustra^ ^F. membranacea^ ^Membranipora^ ^M. pilosa^ ^M. lineata^ ^M. tenuis^ Set ESCHARINA (/Zoœcium wholly calcified/) ^Escharella^ ^E. variabilis^ ^Mollia^ ^M. hyalina^ ^Cellepora^ ^C. scabra^ ^C. ramulosa^ ^C. pumicosa^ Suborder ~CTENOSTOMATA~ (/Horny or gelatinous zoœcia, having tooth-like processes which close the apertures when the tentacles are retracted/) ^Alcyonidium^ ^A. ramosum^ ^A. hirsutum^ ^A. hispidum^ ^A. parasiticum^ ^Vesicularia^ ^V. dichotoma^ ^V. custata^ Subclass =Entoprocta= (/Excretory opening within lophophore; mouth near margin of area, which is surrounded by tentacles; tentacles roll up instead of being retracted/)