Radiocarbon age determinations of fossil Margaritifera auricularia (Spengler) from the River Thames in West London

In the early 1900s shells of a large freshwater mussel, Margaritifera auricularia (Spengler), were discovered in calcreted gravel dredged from the channel of the Thames at several sites between Mortlake and Battersea in west London. These specimens were said to have been associated with Neolithic polished stone axes, supposedly as food remains. M. auricularia is now extinct in Britain, but it has been reported living in several large rivers in southern Europe although apparently not in recent years. Three radiocarbon dates of 4140±50, 4340±45 and 4860±40 bp have been obtained from Thames specimens, supporting a Neolithic age for these shells. The theory that the shells represent debris from imported human food is discounted and it is considered more likely that M. auricularia was actually living in the Thames in Neolithic times. Its extinction in Britain should be seen as part of a general recession during the Post-glacial, as revealed by fossil occurrences to the north and east of its present-day range.     

Seasonal dating and the valve-pairing technique in shell-midden analysis

Three-dimensional excavation of 23 artifact fragments and 4382 shells was carried out in the shell layer of an abandoned dwelling pit. Principal component analysis using three locational variables was used for drawing the central axes and the regression plane of the shell layer. Valve-pairing carried out on the clam Meretrix lusoria indicated that 380 pairs could be established among a total of 2089 unbroken valves. Preservation of shells was estimated at 70% by comparing the number of shells found in the shell layer with the clam population size which was in turn calculated by a probability formula using paired valves among samples. In addition to these data, the distance separating pairs gave some idea of the movement of shells. Seasonal dating by daily growth line counting showed that the shell layer could be subdivided into at least three main seasonal layers and that the period of accumulation was approximately 500 days.     

Michael J Clarke collections,from the Geological Survey of Tasmania,are transferred to the Tasmanian Museum and Art Gallery

Over 300 primary type and figured specimens of Late Palaeozoic invertebrates described by Michael J Clarke have been transferred to the Tasmanian Museum and Art Gallery Collections.