The next paper dates from 1969 and was published in: 'Mededelingen van de Werkgroep voor Tertiaire en Kwartaire Geologie', 6(3): 53-54, 1 fig.
Originally written in Dutch language with an English summary, I here provide an English translation.
Also read this paper! (Dutch text)
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THEODOXUS DANUBIALIS (PFEIFFER 1828) FROM THE FLEMISH VALLEY AT ZELZATE (BELGIUM)
T. Meijer
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SUMMARY
In the collection M. van den Bosch some specimens of the freshwater snail Theodoxus danubialis (Pfeiffer) were found. The specimens were collected at the base of the deposits of the Flemish Valley (younger Eemien) from an exposure near Zelzate (Belgium). Also the specimens of "Theodoxus fluviatilis" mentioned in Janssen 1965 appeared to be T. danubialis. This species has not been found before in the younger Pleistocene of this surroundings.
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Some time ago I noticed in the collection of M. van den Bosch among material which was collected in the tunnel construction pit in Zelzate 4 specimens of the fresh water mollusc Theodoxus danubialis (Pfeiffer, 1828). The identification was based upon the characteristic colourpattern which was still present in one specimen and was confirmed by mr. H.K. Mienis (Amsterdam).
The specimens are found at a depth of 13,60 tot 13,80 m -O.P. from the basal part of the Flemish Valley deposits (late Eemian). The material consists of two fragments which undoubtedly belong to this species, 1 complete specimen without colourpattern (measurements: H 4,9 mm, L 5,0 mm) and a defective specimen showing a large part of the colourpattern (measurements: H 4,4 mm, B 4,7 mm). The colourpattern consists of dark violet zigzag bands on a light-creame coloured background (see fig.).
After examination Theodoxus fluviatilis Janssen 1965 (p.25) non Linné 1758 also proved to belong to Theodoxus danubialis.
In the recent fauna the species has its distribution in the Danube area. It lives on stones in rivers, brooks, lakes and sources.
The species is known from the Pleistocene of Swanscombe (Kent) as T. danubialis cantianus (Kennard & Woodward 1924). In our country it was found in the 'Icenien' from a borehole near the town of Dordrecht (Tesch 1944).
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References:
Janssen, A.W., 1965. Mollusca uit de pleistocene ontsluiting te Zelzate. -- Mededelingen van de W.T.K.G., 2(2): 25.
Tesch, P., 1944. Nieuwe lijst der kwartaire land- en zoetwatermollusken in Nederland. -- Mededelingen 's Rijks Geologischen Dienst, A(10): 3.
