Dancing has its dialects as well as its pure and proper elocution, and not every performer -- no matter how strong -- fits all roles. At the American Ballet Theatre, Mikhail Baryshnikov's regime is showing a sure eye for correct casting. This was certainly the case at the Kennedy Center in both performances Saturday. Classicism was rampant, with two true new Claras in "The Nutcracker" and several others of the company's clearest dancers taking key roles.

Such rosters can't be dismissed as typecasting. Deirdre Carberry, whose debut as Clara was at the matinee, and Cheryl Yeager, who bowed in the part that night, don't look alike or dance alike. What they both create, however, is an effect we call the academic style. It consists of a critical compounding of anatomy and manners.

Carberry is tiny, and probably hasn't a spare ounce. Yet, her gently rounded features and form suggest that she's just outgrown a phase of baby fat. Last month she turned 16, but on stage in the Christmas ballet she was still a wonderful little girl -- warm, spontaneous and polite. In both acts she was very much at ease, moving through mime scenes and passages of dancing softly, with assurance. The audience was richly entertained because, so it seemed, she enjoyed herself thoroughly. If her neck looked short for ideal bearing -- and the rise of the costumes and length of the coiffure may have been at fault -- she often compensated with a fine, high carriage.

Johan Renvall, Carberry's Nutcracker Prince, first appears in mask and armor from the hips up. Only the legs show a human dancer's form. Strong in the thighs, set back from the knees down, with a touch of a bow like Nijinsky's, these legs work with immaculate power. Then, when Renvall's casings fly asunder and the whole body begins to stretch and breathe, he holds himself alert, yet relaxed. To call him a model of deportment fails to suggest how fresh his performance was and how genuine his rapport with Carberry. Was it necessary, though, for him to prove that he is at home in the air by skidding when he touched the ground in the big Act 2 variation? One would think that was made manifest by the leap he would add atop a leap in his patterns of flight.

Cheryl Yeager, as Clara, was like a willow leaf, vibrant in surprising ways. During solos as well as supported adagios she can accelerate suddenly to heighten a step, and she uses this ability with musical wisdom. Her characterization was that of an eager girl. Always she seemed to be asking "why?" until she met her prince, tall Ross Stretton. Then she stood and looked way up into his eyes and, for a moment, the question -- but not the wonder -- ceased. There were times though when their encounter cooled to friendship, and if this was only apparent subliminally, it was because Yeager's vivid phrasing and Stretton's seamless partnering made the dancing more important.

Baryshnikov's cadre of classicists in these performances included Peter Fonseca, Gregory Osborne, Lise Houlton, Christine Spizzo, Lucette Katerndahl, and, on Friday night, Ellen Krafft. Saturday afternoon, a quality impossible to achieve in the role of Clara, that of a ballerina godmother, was brought by Kristine Elliott to the part of the Shepherdess.