Structure of Legion of Mary
The Presidium
The basic unit of the Legion is called a Praesidium, which is normally based in a parish. The Praesidium, usually a group of 3–20 members, meets weekly in its parish.
Curia
The Curia is the next level, each supervising several Praesidia.
Comitium
The next level is the Comitium, which is in charge of several Curiae, usually over an area like a medium city, a Diocese or a part of a province.
Regia
The next level is the Regia, which is in charge of larger territories like a province or state (like in the US and Brazil).
Senatus
The Senatus is the next level, and it generally has control over the Regiae in a very large area, usually a country or a very large territory.
Concilium
The Concilium is the highest level and has its seat in Dublin. It has control over the whole Legion.
Each level of the Legion has the same officer structure:
President, Vice-President, Secretary, Treasurer, Spiritual Director. The last is always of the clergy, but all other offices are held by the lay people. All positions regardless of responsibility are voluntary.