A Federation cargo vessel was a class of cargo vessel operated by the Federation during the mid-23rd century that was used for hauling radioactive ore. Due to the nature of its function, the ship's hull was transport resistant and was equipped with minimal life support.
The colonists of Finibus III had access to one such vessel in 2259, and roughly a hundred survivors of the Gorn massacre there escaped the planet aboard it. The ship, represented by Professor Thandie, was allowed to escape to be used as bait by the Gorn to lure in the USS Enterprise. The cargo vessel was not immediately identified by the Enterprise, and when initially encountered, was recognized as an "unidentified ship" with raised shields, "no Federation badges," and multiple unidentified lifeforms aboard, but did not initially respond to hails. Once the cargo vessel's passengers were sure they were being contacted by a Starfleet vessel, they responded, noted that their condition, and agreed to evacuate to Enterprise via deep space transport tube.
Once the passengers were evacuated, and while the Enterprise was still vulnerable due to the attached transport tube, a Gorn hunter emerged from behind the second moon and destroyed the cargo vessel, the transport tube, and caused significant damage to the Enterprise, which was initially unable to raise its shields. (SNW: "Memento Mori")