. Introduction to zoology; a guide to the study of animals, for the use of secondary schools;. TD. -- FIG. Ki). — A, advanced embryo of Anodonta: B, free glochidium. /, pro-visional byssus ; s, sbell; .s7t, books ; .sm, adductor muscle ; so, sense organs;w, cilia. From Korschelt and Heiders Embryology. the adult; the gills arise, the shell gains its adult char-acter, and becomes free from the fish on which it has livedtemporarily as a parasite. There are other species of fresh-water lamellibranchsbesides the Unionidae. These belong to the Cycladidae,allies of the marine Cardidre or Veneridre.
. Introduction to zoology; a guide to the study of animals, for the use of secondary schools;. TD. -- FIG. Ki). — A, advanced embryo of Anodonta: B, free glochidium. /, pro-visional byssus ; s, sbell; .s7t, books ; .sm, adductor muscle ; so, sense organs;w, cilia. From Korschelt and Heiders Embryology. the adult; the gills arise, the shell gains its adult char-acter, and becomes free from the fish on which it has livedtemporarily as a parasite. There are other species of fresh-water lamellibranchsbesides the Unionidae. These belong to the Cycladidae,allies of the marine Cardidre or Veneridre. They havemuch the shape of our common hard-shell clam of the sea,but are much smaller in size, rarely exceeding 15 milli-metres. Cyclas (or Sphserium) is of world-wide distribu- THE FRESH-WATER CLAM AND ITS ALLIES 181 tion, but it is especially abundant in North America. Itoccurs in ditches, ponds, and riversof New England, as well as in theSouth and West Some species ofit inhabit brackish water. Pisidiumhas both valves unsymmetrical. Itsspecies are still smaller than thoseof Cyclas, rar
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1900
