Marine platoon would be larger than the rifle one, as rifle sections consist out of 2 fireteams+leader (9 men) while Marine sections are formed by 3 fireteams + leader.
... here. Weakipedia, I know...
http://en.wikipedia.org/wiki/Organiz...ombat_Elements
So from various sources, a platoon has three sections, 13 men each, plus 4-man HQ element, ie all in all some 43 men counting yourself.