thiadens a a (5 Ergebnisse)

paperbound, 8vo 114 pp. democratisering; zeer goede conditie.

11 S., 3 Abb., 1 Taf., Sprache: Deutsch Gewicht in Gramm: 500.

On a sandy beach of the Dutch North Sea coast an experiment was carried out with 24000 brightly coloured artificial shell valves of Donax vittatus. Unperforated and perforated (artificial Natica-holes of 1, 2 or 3 mm inner diameter) left and right valves of three sizes (19.7, 24.2, and 28.7 mm shell-length) were used. It appeared that under the influence of waves and water currents a clear selection occurred according to size ("size effect"), symmetry ("left-right phenomenon"), presence or absence of a hole ("hole effect"), and diameter of the hole ("diameter effect"). The implication of these observations for studies of the biology of Naticid snails based upon valves collected along the beach are discussed. Furthermore, some remarks are made on the implications of this type of experimental work for sedimentology and marine palaeontology in general. 35 pp., 12 figs, gr. 8.

Kosmos, 1976. Gebonden. Hardcover. 21 x 26 cm. Met illustraties in z/w. 134 pag. UITSTEKEND EXEMPLAAR [Handwerken ].

0. 4to. 80 S., 1 Taf., 2 gefalt. Taf., 1 gefalt. farb. geolog. Karte. - Diss. Sprache: Englischg - Diss. 0.500 gr.