I would also be interested to get new information on that subject. As far as I know from 
my work on the comprehensive edition of the works of Marx and Engels, Marx has not 
dealt in detail with the works of Jevons or Menger. Of course, he was a curious and 
well-informed contemporary, so it is reasonable to assume that he perhaps knew more 
about those directions of political economy than what is reflected in the evidence which 
has survived. 

Anyway, Marx did actually not abandon work on "Capital" in the 1870s, but returned to 
his work time and again, at least until 1881, shortly before his death. With regard to the 
manuscripts, most of them deal with subjects of the second book of "Capital". He also 
produced a lot of excerpts on varied subjects, more or less in connection with his 
"economics", for instance on credit, money, banks etc. 

Regina Roth