An ecclesiarch is the same as the Russian "ustavshchik". He is the one who is responsible for opening up the Typicon and interpreting all the rubrics for the services. (Nowadays various churches publish these rubrics, so there is no real need of an ecclesiarch any more, unless one does not have access to these printed rubrics.) He (or she) is also responsible for locating all the hymns in the books, book-marking them and setting them out on the analogia (reading stands) or chanting stands as they are needed. He also selects competent readers to cover the parts, but should not show any favoritism. In some places the ecclesiarch is the one who announces the Tones (and Special Melodies) of the hymns, as well as the first few words of text, but his duties should not coincide with those of the canonarch.
A paraecclesiarch (called a "ponomar" or "ponomarshchik" in Russian) is one who cleans the church and is responsible for the oil lamps and candles. He typically is the warden (i.e. he has the church keys and is responsible for unlocking and locking the church, and is responsible for ringing the bells. He also helps with placing icons on stands and arranging flowers around them, helping to set up the baptismal font or container for blessing water, etc. Basically he helps with anything going on in the vestibule and nave, although he has to enter the altar to clean it and light the oil lamps. In monasteries, the paraecclesiarch must always get a blessing before performing his duties, but in parishes this is frequently an appointed or volunteer position with a small monetary stipend. The modern Russian "starosta" performs some of these duties, but the position is usually limited to that of a "door warden" or "usher".
Nikita Simmons, January 2007