LOS ANGELES -- NBC Entertainment president Brandon Tartikoff and News division president Larry Grossman delivered their State of the Network speeches yesterday before about 65 TV writers and, as you might well expect from the primetime leader, they made pretty positive Statements . . .

Tartikoff, the funniest Entertainment president in the business, was, well, almost Statesman-like yesterday, confining himself to a lot of announcements and only a few jokes.

Oh, he allowed himself to be picked up and carried around the stage by some character named Jacko, who will join Sam Jones on "The Highwayman," the new kiddy adventure series that debuts March 4 in the Friday, 8 p.m., time slot ("He's a little heavy; it must be the wallet," said Jacko, who was discovered in the Energizer battery commercial, unfortunately).

And we even heard Tartikoff use the word "perforce," surely a network executive first. But generally he was pretty low key . . .

From the top, Tartikoff announced a new weekly, one-hour all-family-viewing series for next winter to be hosted, written and produced by Muppetmeister Jim Henson . . . titled appropriately enough "Jim Henson Presents" . . .

Tartikoff also revealed that Ben Vereen will join the cast of "J.J. Starbuck" as of Saturday, Feb. 20, as a co-star with Dale Robertson. The Surprise: Vereen will be reprising his role as "Tenspeed" Turner, from the 1980 series "Tenspeed and Brown Shoe" . . .

NBC has also purchased the rights to the young-adult best seller "Sweet Valley High," which will start as a two-hour special but will probably become a series ...

The network will launch a talent search for female identical twins, 15 years and older, to play the beautiful 16-year-old Wakefield twins in the Francine Pascal story (photo submissions only should be sent to SVH/NBC Productions, 4640 Landkershim Blvd., Fourth Floor, North Hollywood, Calif. 91602, if you are a twin and happen to be interested) . . .

NBC will probably air a primetime serial this summer but no details were given . . .

Tartikoff promised that "the momentum will continue" for the network, which has finished first in primetime every week except one since last year's Super Bowl . . .

He was especially proud of how well the second-year series "ALF," "L.A. Law," "Matlock" and "Crime Story" have performed this season . . .

Moving Right Along

Tartikoff said "The Days and Nights of Molly Dodd" will be back on the schedule after the February sweeps. Six episodes have already been completed ...

He cautioned, however, that the critical interest in so-called "dramadies" like "Molly Dodd," which eschew laugh tracks, perforce, may not signal a big increase in the genre . . .

Hinting that he thinks they're the work of comedy writers suffering from a lack of jokes, he added, "I can understand a comedy without a laugh track, I can't understand a comedy that isn't funny, or doesn't tell a story . . . I don't see somebody remembering an episode of {CBS'} 'Frank's Place' in a couple of years and saying, 'Yeah, that was really poignant.' "

He said a pilot of "90 Minutes," the elusive project that will combine talent and input from the NBC Entertainment, News and Sports divisions for the early Sunday night slot, smack against CBS' "60 Minutes," is now scheduled for April 10.

The series, if it works, won't debut until early 1989 however . . .

Tartikoff admitted some dissatisfaction with the Cosby spin-off "A Different World," saying "adult appeal was lacking in the first 13 episodes" ...

He said the recent addition of three characters will probably help the series. Meanwhile, he noted, "the writing is getting there, inch by inch," something short of a ringing endorsement, when you think about it . . .

He said that Michael J. Fox had "indicated an interest in one more year" with "Family Ties" during the show's Christmas party . . .

But he said "we've only talked about" any chance of Bill Cosby returning for a fifth year of "The Cosby Show." He said the No. 1 network show has "cooled off" from a 55 to a 47 percent audience share so far this season . . .

With "The Highwayman" moving into 8 p.m. Fridays against CBS' "Beauty and the Beast," he predicted that ABC Entertainment may move the popular "Growing Pains" from Tuesday to 8 p.m. Friday soon, too.

Tartikoff said that the 8 p.m. Friday slot "is crying out for an action show," which bodes ill, if he's right, for "Beauty and the Beast," which has leveled off after a period of growth and good reviews . . .

Tartikoff also hinted that at least three series may be nearing an end of the run -- "Highway to Heaven" and "Miami Vice" are both "trending down," he noted, while MTM Productions is worried about a lack of interest in "St. Elsewhere" as a syndication possibility . . .

In Other News

NBC News president Larry Grossman, in his remarks, said the growing possibility of a brokered nominating convention for the Democrats may increase the amount of coverage this summer, but stopped short of promising gavel-to-gavel coverage . . .

He also said that should one party receive an unusual amount of coverage, say 30 hours, that would not necessarily guarantee equal time for the opposing party's convention. He promised that NBC News would show "a sense of fairness," and that "we are prepared to give as much coverage as is editorially and journalistically sound" to either convention . . .

He also downplayed rumors that Bryant Gumbel, whose contract ends late this year, would not be returning to the "Today" show. "It's much too early to talk about that," said Grossman . . .

Fox Broadcasting has canceled "The Wilton North Report" as of tomorrow night's broadcast . . .

The late-night entry has been ripped by critics and ignored by viewers . . . It will be replaced temporarily by reruns of "The Late Show," to be called "The Best of the Late Show With Arsenio Hall" . . .

And starting Monday, CBS' "60 Minutes" correspondent team will start making appearances on "CBS Evening News With Dan Rather" . . .

Rather and CBS News president Howard Stringer have been talking up such a rotation of talent for months, although "60 Minutes" executive producer Don Hewitt reportedly remains lukewarm about the extra workload for his troops . . .

Senior correspondent Mike Wallace is tentatively scheduled to kick off the new rotation next week.

Diane Sawyer, Ed Bradley, Morley Safer and Harry Reasoner are also due to appear with "perspective reports" on the news . . .

NBC's "Ann Jillian Story," in which the actress dramatized her own successful battle against breast cancer, showed up with the highest audience share for a TV movie on any network this season . . .

The Monday night entry had a 23.8 Nielsen rating and a 35 percent audience share . . .