Cite, please, on where the Corps was part of the Army until 1834.
Weren't the Corps formed in a Philly tavern to protect privateers before there was a ground army?
The Marine Corps Birthday was celebrated then until between the world wars.
http://hqinet001.hqmc.usmc.mil/HD/Historical/Docs_Speeches/OrganizationofUSMC.htm
That law was put into effect on 11 July. Before then, the Marines were part of the Army except when detached for sea service.
Presley O'Bannion was recruited as an Army Officer, then detached to the Navy with some 8 other guys and 300 mercenaries.
"SEC 4. And be it further enacted, That the officers, non-commissioned officers, privates, and musicians, aforesaid, shall take the same oath, and shall be governed by the same rules and articles of war, as are prescribed for the military establishment of the United States"
http://hqinet001.hqmc.usmc.mil/HD/Historical/Docs_Speeches/Establishingamarinecorps.htm
The Marines were part of the Army, unless on active sea service. So when O'Bannon landed, he was under the Articles of War, and fought as a unit of the Army.