Matt Ridley's take on the definition of species selection:

``Species selection is a higher level analog of normal natural
  selection within a population.  Species selection means, other
  things being equal, that those kinds of species that have lower
  extinction and higher speciation rates will tend to increase in
  frequency over evolutionary time.''

 - Evolution (the textbook), Matt Ridley, 3rd edition, p. 665.

As far as I can see, this is the perfectly natural and
conventional definition of species selection - one based
on the actual differential reproductive success of species.

Note that there is no mention at all of whether the 
differential reproductive rates could also be explained
in terms of selection at a lower level.

Ridley uses a similar definiton for group selection -
on p.303 - citing Wade's Trifolium experiments as
an example of group selection under laboratory conditions.

This used selection for low fecundity - a fairly clear
example of a trait where the property of the group
is the additive result of individual properties.

It seems to me that those who favour other definitions
of group and species selection - involving whether the
effect could also be explained at a lower level - still
have textbook authors to convince - in addition to me
and a number of other sceptics.
-- 
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