The Gemara talks about ways avoid the Isur of Muktzah while carrying a moneypurse that was left in Reshus ha'Rabim before Shabbos. Rashi points out that besides the problem of Muktzah, one must avoid carrying in Reshus ha'Rabim by moving the purse less than 4 Amos at a time (and not bringing it into Reshus ha'Yachid).
On 17b the Gemara mentioned a Gezeirah that one must give his purse to a Nochri, if he finds himself in middle of the road before Shabbos. Rashi there explains that the Gezeirah was, that one may not carry the purse less than 4 Amos at a time. Rather he must give it to a Nochri to carry.
Why, then, did the Amora'im in our Gemara permit moving the purse less than 4 Amos at a time!
Q. Reese, Atlanta, Georgia
The answer to your question is easily understood by looking at the Shulchan Aruch (O.C. 266:1-7).
The Shulchan Aruch starts out with a case of someone who realizes that he is not going to make it to where he wants to go before Shabbos. How does he get his money home? The very first option is that *if* he has a Nochri with him, he must give the purse to the Nochri and not use the leniency of carrying less than four Amos at a time, which Chazal only permitted in certain situations (being that a person can come to easily transgress a Melachah d'Oraisa if he is not careful).
The Shulchan Aruch continues to give other preferable options before stating (226:7) that if none of the aforestated ways to transport the money are available, one can use this method of carrying. Rashi in our Gemara was talking about a case when transport via a Nochri was not an option. [The Gemara seems to make this the case, as according to Rashi the Gemara later says that this was also how the money was moved in a Sratya, which Rashi explains means a Reshus ha'Rabim. If there was a Nochri available they would have asked him to move it.]
All the best,
Yaakov Montrose