Bouchet & Rocroi, on page 271 ( 2005 ), also state that the assignation of " " symmetrical univalved mollusks " bellerophonts " either to Gastropoda or to Monoplacophora or Tergomya is controversial . ""
12.
The earlier name " univalve " means " one valve " or shell, in contrast to " bivalve " applied to mollusks such as clams and meaning that those animals possess two valves or shells.
13.
A number of terms are used to describe molluscan shell shape; in the univalved molluscs, endogastric shells coil backwards ( away from the head ), whereas exogastric shells coil forwards; the equivalent terms in bivalved molluscs are opisthogyrate and prosogyrate respectively.
14.
At first this dung is a poor source of nutrition, and so univalves pay no attention to it, but after several days, micro-organisms begin to multiply on it again, its nutritional balance improves, and so they eat it again.
15.
In 1840 he began the publication of his monograph on the Fresh-Water Univalve Mollusca of the United States, in which he described the " Scolithus linearis ", a new genus and species of fossil plant, the most ancient organic remains in Pennsylvania.
16.
Gastropoda ( previously known as "'univalves "'and sometimes spelled " Gasteropoda " ) are a major part of the phylum Mollusca, and are the most highly diversified class in the phylum, with 60, 000 to 80, 000 living snail and slug species.
