THE occurrence of greywacke in the Lower Siwaliks has recently been commented on by Sikka et al.¹, and taken as evidence that â the notion that the Siwaliks are entirely of freshwater origin may no longer be trueâ . This conclusion is opposed to a great mass of palæontological data in which there is not the least suggestion of a marine environment. This was pointed out by Ganju and Srivastava², who went on to suggest that â much of the so-called greywacke of the Siwaliks may, in fact, turn out to be sub-greywacke (the low-rank greywacke of Krynine) if a proper petrographic study is made. If this is the case [they say], the notion that the Siwaliks are entirely of freshwater origin may still be true, because the sub-greywackes are neither necessarily marine nor are they confined to the geotectonic beltsâ .