Yale’s 310th Commencement had the robes and vocabulary of a formal ceremony, but graduates added their own flavor to the proceedings with spirited shouts and accessories.

Yale University conferred 2,907 degrees — 1,251 to undergraduates — and awarded another 229 provisionally to students in the Law School and in the School of Medicine’s Physician Associate Program, who have not yet completed their courses of study. Provost Peter Salovey also announced to a crowd that filled the roughly 18,000 seats on Old Campus the recipients of ten honorary doctorates, a group that included former U.S. Senator George Mitchell, Academy Award-winner Martin Scorsese, and acclaimed author Joan Didion.

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According to tradition, yesterday’s Class Day saw a myriad of unusual hats — including cheese heads, a toilet bowl and a Mory’s cup — but many graduates wore festive head wear and accessorized according to their Yale affiliations on Sunday as well. Silliman College’s seniors waved foam batons imprinted with the name of their college, and Branford seniors pasted pieces of paper to their mortarboards imprinted with the phrase “S. Diddy’s Crew,” in reference to departing master Steven Smith.

Graduate and professional school students, who wore black robes with colored hoods, chose fashions more closely related to their specialties.

Many graduates from the School of Forestry & Environmental Studies paid tribute to their specializations with special decorations on their hats. Standouts included small forest fires, waves and a functioning solar panel. Jamie Pool FES ’11 precariously balanced a set of antlers and a globe on his head because he said he is the rare environmentalist who also hunts.

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A group of midwives who wore baseball mitts and baby dolls on their mortarboards stood out among their peers from the Nursing School.

“We’re baby-catchers,” one student said.

Though most graduates receive their diplomas at individual ceremonies for their schools or residential colleges after Commencement, representatives for each received degrees from University President Richard Levin.

Undergraduates stood up to scream for their respective representatives, and Matt Kremer ’11 roused his fellow Saybrugians when his “Say what?” from the stage was answered by a rousing “Saybrook!”

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On Sunday’s Class Day, Yale College Dean Mary Miller led the students of Yale College in rehearsing the “loud explosion” she wanted to hear after asking University President Richard Levin to confer degrees on them the next day. But the class of 2011 erupted into cheers and started waving pennants only halfway through her presentation at Commencement. A few moments later, though, the seniors followed the actual end of her speech with an even louder roar.

Undergraduates began the ceremony with fanfare, entering Old Campus through Phelps Gate behind a marching band, flags carried by student award winners and Acting University Librarian Jon Butler, chief

marshal for the ceremony and former dean of the Graduate School. This marks the first year that Butler carried the University’s 117-year-old mace as chief marshal. He replaced former Deputy Provost Charles “Chip” Long in the role.

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Thomas Pollard, who became dean of the Graduate School last summer, also entered the ceremony in a new role. He labored through the Latin-language presentation of philosophy students, though he still garnered a hefty roar from the crowd.

As Levin presented honorary doctorates to this year’s recipients, he reminded the Yale graduates that the citations are meant to “encourage you and inspire you to excellence.” The ten luminaries are trailblazers in fields ranging from film to journalism to medicine. Senegalese musician Youssou N’Dour was awarded an honorary doctorate of music alongside former Prime Minister of Norway Gro Harlem Brundtland, who received an honorary doctorate of humane letters. Brundtland served as Director-General of the World Health Organization from 1998 to 2003 and led the response to the global Severe Acute Respiratory Syndrome outbreak during her tenure at the WHO.

Douglas Engelbart, who invented the computer mouse, teared up after he was introduced as the recipient of Yale’s first honorary doctorate for engineering and technology.

“We touch your genius every day,” University President Richard Levin said in his citation for Engelbart to chuckles from the audience. “As the inventor of the mouse, you put computing in our hands.”

Despite chilly temperatures and overcast skies, spectators stayed dry for the ceremony. Vendors braved the threat of rain to sell flowers, balloons and stuffed animals on street corners around Old Campus.

Dan Sullivan, who was selling balloons and stuffed animals on the corner of High and Elm Streets and has sold novelties at various graduations across Connecticut, said after the ceremony that business had been “good,” even though the number of competing vendors has increased steadily in the 11 years that he has come to Yale to sell his wares.

Yale’s Commencement moved to Old Campus from Woolsey Hall in 1950 to accommodate an increase in the size of the University’s graduating classes.

For more coverage read our live blog from the event.