The chief Pre-Chellean and Chellean stations were clustered along the valleys of the Somme and Seine. Of those rare sites presenting a typical Pre-Chellean culture, we may note the neighboring stations of St. Acheul and Montières, both in the suburbs of Amiens on the Somme, and the station of Helin, near Spiennes, in Belgium, explored by Rutot. A very primitive and possibly Pre-Chellean culture was found on the site of the Champ de Mars, at Abbeville. This culture also extended westward across the broad plain which is now the Strait of Dover to the valley of the Thames, on whose northern bank is the important station of Gray's Thurrock, while farther to the south is the recently discovered site of Piltdown, in the valley of the Ouse, Sussex. The flint tools (Fig. 60) found in the layer immediately overlying the Piltdown skull are excessively primitive and indicate that the Piltdown flint workers had not attained the stage of craftsmanship described by Commont as 'Pre-Chellean' at St. Acheul. "Among the flints," observes Dawson, "we found several undoubted flint implements besides numerous 'eoliths.' The workmanship of the former is similar to that of the Chellean or Pre-Chellean stage; but in the majority of the Piltdown specimens the work appears chiefly on one face of the implements." [Illustration: FIG. 61. Primitive _coups de poing_ or 'hand-stones' of Pre-Chellean type, found in the lower gravels of the middle and high terraces at St. Acheul. After Commont. One-quarter actual size.] In the Helin quarry near Spiennes(13) occur rude prototypes of the Palæolithic coup de poing associated with numerous flakes which do not greatly differ from those in the lowest river-gravels of St. Acheul; there is a close correspondence in the workmanship of the two sites, so that we may regard the Mesvinian of Rutot[X] as a culture stage equivalent to the Pre-Chellean. The river-gravels and sands of Helin which contain the implements also resemble those of St. Acheul in their order of stratification. Of special interest is the fact that a primitive flint from this Helin quarry, known as the 'borer,' is strikingly similar to the 'Eolithic' borer found in the same layer with the Piltdown skull in Sussex. By such indications as this, when strengthened by further evidence of the same kind, we may be able eventually to establish the date both of this Pre-Chellean or Mesvinian culture and of the Piltdown race.