"The Lorelei Signal" and The Eye of the Beholder (1974) are the only times in any Star Trek incarnation when Lieutenant Uhura assumes command of the Enterprise.
The title of this episode is a reference to the Legend of the Lorelei, which is an old German tale of a beautiful woman who lured sailors to the Rhine causing them to crash on the rocks - analogous to the sirens of Ancient Greek mythology.
The planet name, Taurus II, appears to be the same name as the hostile planet a party led by Spock crash-landed on in The Galileo Seven (1967) from the original live-action series. "The Star Trek Concordance", (c) 1975, tried to explain this apparent inconsistency by mentioning that even on 20th century earth there were wild, untamed regions where, if a space traveler landed there, they would find it hard to believe that places such as London or Paris existed on the same planet.
This installment marks the only time in the history of the franchise where Uhura can be heard saying "Phasers on stun....Fire!"