Does the first portion of a trip that was < 50nm count as XC on a long trip?
The relevant regulation is in 14 CFR 61.1(b)(3):


  Cross-country time means—
  
  (i) Except as provided in paragraphs (ii) through (vi) of this
  definition, time acquired during flight—
  
  (A) Conducted by a person who holds a pilot certificate;
  
  (B) Conducted in an aircraft;
  
  (C) That includes a landing at a point other than the point of
  departure; and
  
  (D) That involves the use of dead reckoning, pilotage, electronic
  navigation aids, radio aids, or other navigation systems to navigate
  to the landing point.
  
  (ii) For the purpose of meeting the aeronautical experience
  requirements (except for a rotorcraft category rating), for a private
  pilot certificate (except for a powered parachute category rating), a
  commercial pilot certificate, or an instrument rating, or for the
  purpose of exercising recreational pilot privileges (except in a
  rotorcraft) under §61.101 (c), time acquired during a flight—
  
  (A) Conducted in an appropriate aircraft;
  
  (B) That includes a point of landing that was at least a straight-line
  distance of more than 50 nautical miles from the original point of
  departure; and
  
  (C) That involves the use of dead reckoning, pilotage, electronic
  navigation aids, radio aids, or other navigation systems to navigate
  to the landing point.


Note that the rule under paragraph (ii)(B) is "a flight" that includes "a" point of landing more than 50nm from the point of departure.  It does not specify that all points of landing must be further than 50nm from the departure point, or even that the first point of landing must be further than 50nm.

Since the overall trip was over 50nm, does the FAA allow you to consider that 24nm leg to be part a single overall flight?  Unfortunately, the FAA doesn't provide a definition of "flight" in this context.  However, it is generally accepted that short stops (to pick up a passenger, refuel, eat lunch, etc.) can be logged as part of a single flight.

Edit to add:  Please also this this previous question, and especially the AOPA article it links to.