Rawlins was a Starfleet officer who lived during the mid-23rd century. They served in the sciences division aboard the USS Enterprise under Captain James T. Kirk, during Kirk's historic five-year mission. In 2268, Rawlins was assigned as the ship's chief geologist.
That year, Rawlins was recommended to be among the landing party by Captain Kirk to planet Alpha Carinae II. However, the M-5 multitronic unit recommended Ensign Carstairs over Rawlins as the former had visited the planet on a geology survey for a mining company while serving in the Merchant Marine. (TOS: "The Ultimate Computer")
This character was only mentioned in dialogue.
The Star Trek Encyclopedia (4th ed., vol. 2, p. 207) spelled this character's name as Rawlens.
The novel A Choice of Catastrophes gives his first name as "Niall". In the episode's novelization, the mentioned geologist was named Rawls.