The D.C. statehood constitutional convention opened officially yesterday amid ceremonial pomp and calls by the city's political leaders for the diverse group of 45 delegates to close ranks for the long march to greater autonomy.

Mayor Marion Barry called the convention to order before an invitation-only crowd of about 700 at the Dunbar Senior High School auditorium and urged the delegates to get straight to the business of writing a constitution for the District.

"Some of us came over on a ship called home rule," Barry said, acknowledging the differences that have existed here over how best to increase autonomy for the city. "Some of us came over on a ship called constitutional amendment. And some of us came over on a ship called statehood. Well, whatever ship we came over on, we're in the same boat now."

"This is an historic moment," said D.C. City Council member Hilda Mason, a convention delegate and the council's lone D.C. Statehood Party member. "Some said we'd never reach the point of writing a constitution."

The delegates--62 percent black, 40 percent female and comprising a wide variety of blue-collar workers, bureaucrats, teachers, poverty workers, lawyers and a handful of political radicals--will hold their first business meeting today in the City Council chambers at the District Building.

The constitution they are charged with writing likely will be presented to the city's voters in this fall's elections. If it is accepted there, it will go to Congress for approval, the last formal step in achieving statehood.

The $150,000 convention is scheduled to last 90 days, plus a preliminary organizing period of up to two weeks. Though officers and committees still have not been established nor a working schedule set, several delegates said they expect many of their meetings to be at night and on weekends because so many delegates hold regular weekday jobs and cannot leave them. The convention sessions generally will be open to the public.

At yesterday's ceremonial opening, Barry and other city leaders praised the occasion as "historic" and "momentous" but were cautious about predicting whether the convention would achieve statehood.

Barry called the convention a bid for "political equity." Walter E. Fauntroy, the District's non-voting representative in Congress, called it a "new chapter in our continuing struggle for self-determination."

Fauntroy, who is known to have doubts about the economic viability of District statehood, has been pushing a constitutional amendment to give the city full voting rights in Congress.

"Some say full voting rights is incompatible with the statehood movement ," he told the delegates yesterday. "Well, what we're saying is: pass the buck--full self-determination for the citizens of the District of Columbia."

At another point, Barry compared District citizenry to a caged bird. "How can a caged bird sing?" he said. "Because that caged bird knows that one day it will be free."

Yesterday's program was dedicated to the late Julius Hobson, one of the founders of the D.C. Statehood Party, a former City Council member and longtime civil rights activist who died in 1977.

Mason said Hobson's "spirit is here." At another point, the audience at the high school stood for a moment of silence in Hobson's memory.

The crowd, racially mixed and sprinkled with city officials, applauded when Barry and Fauntroy recalled the long, bitter years of the civil rights movement and the slow attainment of federal legislation to assist blacks in the South. They said the same kind of slow process is to be expected in the drive for autonomy for the District.