The Dallas Mavericks rode officially into the National Basketball Association yesterday, wearing a good-guy white cowboy hat hanging on an italic block, blue M superimposed over a green basketball by way of logo.

Commissioner Larry O'Brien was there to sign into the league the prize occupant of the 19,000-capacity Reunion Arena that opened this week.

Norm Sonju, former Buffalo NBA general manager putting the outfit together for owner Donald Carter, said he and aide Rick Sund will conduct the club's first draft themselves, waiting at least 30 days before hiring a coach.

NBA's Houston Rockets aren't looking for a coach. Owner George Maloof just gave Del Harris a three-year extension . . .

Another reason, maybe, Athletic Director Vince Dooley of Georgia had a mildly Cheshire-cat air on his visit here last week: Coach Hugh Durham was in the process of hauling in prime timber of Bulldog basketball in James Banks, 6-5 Atlantan who led Smith High to the state Class AAA title, averaging 24-7 points, 14.3 rebounds, etc. etc. as a senior and becoming the target of abortive campaigns by Maryland's Lefty Driesell and North Carolina's Dean Smith . . .

Sen. David Pryor (D-Ark.) and Rep. Bruce Vento (D-Minn.) introduced companion bills in the House and Senate yesterday to prohibit nationwide drugging of horses prior to races. Pryor cities Arkansas' restrictive laws and a virtual end to breakdown during races at Oaklawn Park in Hot Springs, where all prerace medication is banned except Lasix for bleeders. The measure, he said, seeks "an end to the practice of administering pain-killing drugs to injured horses to enable them to race beyond their physical capabilities" . . .

The names of nine jockeys, several of them among the most prominent in U.S. thoroughbred racing, are expected to surface after the race-fixing trial of former jockey Con Errico, 58, opens May 12 -- and the New York Post already has published nine names. "Pure speculation, at this point," comments a spokesman for the New York Racing Association on the reports about alleged bribes to hold back horses at Aqueduct and Saratoga in 1974 and 1975. "The policy of the association is that when indictments are handed up, those indicted will not be allowed to ride". . .

George Mason's turn to host a banquet next Wednesday, 7 p.m., Country Club of Fairfax ($25 donation, contact Jay Marsh), this one to welcome Joe Harrington, the new hoop coach. It'll be like Maryland Terp old home week saluting the ex-Terrapin: John Lucas as M.C., Tom McMillen quest speaker. . .

Man in a white hat? Actor Glenn Ford confirms he has ridden to the rescue of the NHL's Atlanta Flames with a $14 million offer to take the losing proposition off owner Tom Cousins' hands -- and keep the franchise where it is, "one of my favorite cities." That's Canadian-born Ford, trying to beat calgary to the draw. . . Hot (?) Boston rumor: Gerry Cheevers next Bruin coach. . .