Lance Corporal
From Starbase 900 Wiki
Lance Corporal is the third enlisted rank in order of seniority in the Starfleet Marine Corps, just above Private First Class and below Corporal. It is not a non-commissioned officer rank. Promotion to Lance corporal is based on time in-grade, time in service, and the conduct of the marine. Further promotion to the NCO ranks (Corporal and above) is competitive and takes into account the individual service record of the marine. There can only be a certain number of Corporals and Sergeants in each MOS, so even with a qualifying cutting score promotions may be delayed due to an excessive number of Corporals occupying billets in a certain MOS.
Lance Corporal is equivalent in rank to Crewman.