There will be important a cast addition to The Cocoanuts when the Marx Brothers antic moves up July 27 from the American Jewish Theatre to the American Place Theatre--specifically, a canine on the smallish, talented side.

St. Bernards--director Richard Sabellico cautions sternly--will not be seen.

What he is hunting for is an extremely talented dog to perform tricks onstage, follow people onstage, cross the stage alone and mix it up the pseudo-Marxes.

There is also, now, a crying need for a cat in the show, but the requirements are not as stiff. In fact, a stupid cat might suffice. "It's basically a modeling gig for the cat," says Sabellico. The (hopefully) docile feline will be carried onstage in a birdcage and just sit there. That's the whole role.

Auditions for the dog and cat parts will be held from 10 AM to noon at the American Jewish Theatre (307 West 26th St.), and rehearsals start immediately. Alec Timerman has replaced Richard Rolan as the male ingenue, but otherwise the AJT cast remains the same. Making their marks as latter-day Marxes are Michael McGrath (Groucho), Peter Slutsker (Chico) and Robert Sapoff (Harpo).