Eventually it seems that the story about this reference runs as follows:

Hayek, von Mises and Bohm Bawerk were translated into Spanish by two 
brothers - Joaquin and Luis Reig Albiol.

Joaquin translated inter alia Human Action and develops in a footnote 
the influence, alledged by Mises of  marginalism on the non publication 
of Capital (after 1867) (The book is intitled in Spanish Accion Humana 
and went through three edition (1960, 1968, 1980). A translation of  the 
part XII of the first volume of Bohm Bawerk Geschichte und Kritik der 
Kapitalzinstheorien. was later published with the title La teoria de la 
explotacion [Madrid] : Mirasierra, etc. , [1976]. The preface is signed 
"J.R." - obviously Joaquin Reig Albiol. The conclusion of this preface 
is essentially the same as in  the footnote of the Accion Umana. Joaquin 
Reig explainedthat Marx was a prolific author in economics till 1867 and 
then added  : "Many people think that his silence after is due to the 
publications in 1871 by Jevons (Theory of political economy) and Menger 
(Principles of Political economy)" (p.33).

Summung up, Mises and/or Reig Albiol supplied no evidence about any link 
between Jevons or Menger Marx. In the "Fatal Conceit" Hayek obviously 
quoted Joaquin Reig who has developped some elliptic sentences of Mises.

End of the story unless Luis Joaquin Reig has developped the connection 
between his brothers Reig, Hayek and von Mises.

(Thanks to Teresa Garcia Merino for her help.)

PS : The elaboration of Volume III is finely analyzed  in the 
International journal of political economy Spring 2002  Vol. 32 No. 01
(Guest Editors: Regina Roth & Fred Moseley)

Alain Alcouffe