Jonathan Shahn's bronze portrait heads and busts at Addison/Ripley Gallery are both classic and contemporary. His work is an amalgam that recalls both Florentine sculpture of the Renaissance and, more obliquely, plasters by George Segal, though any suggestion that Shahn takes casts from life--as Segal does--makes him mad.

"This isn't George Segal, you know," he'll say. "I carved these things."

And how he carves them! There is, among these 14 works, a masterpiece: a half-length bronze portrait of an elegant young woman, her hand extended and resting upon the slab that cuts her off at the waist. Her features are exquisite--high cheekbones, thin aquiline nose--and they are rendered with such sensitivity that her skin and delicate nostrils, though made of bronze, take on the translucence of Renaissance marbles.

Though this piece depicts a very specific person--in this case a 13-year-old girl of mixed German and Egyptian descent--it also transcends portraiture with a timelessness that is typical of Shahn at his best. There are other examples: a bust of a young woman whose face has the monumentality of a Benin bronze and a full-size plaster of a nude model.

The contemporary twists dawn more slowly on the viewer, adding a crucial conceptual dimension. Several heads, for example, are depicted as works in process, impaled on the studio armature, with clumps of clay and modeling tools included in the casting. They seem to live and breathe, until the unfinished necks remind us that they are only clay--a metaphor for art as well as life. Shahn also uses words (made from rubber stamps pressed into the clay) to pull his works back from the past into the present.

The 48-year-old Shahn, son of the great American painter Ben Shahn, recently returned from Rome, where he spent nine years working and teaching at the Tyler School. Trained at the Boston Museum School, he now teaches at the Sculpture Center in New York, where he exhibited in 1982. Of changes since his last Washington show in 1966 (at the now-defunct Hinckley-Brohel Gallery), Shahn will only say, "I am better now." It is high time the world took notice. His show continues through April 16. Ella Tulin at Addison/Ripley

The first gallery you enter at Addison/Ripley is currently filled with the work of another sculptor--the prolific Ella Tulin, a Washington art therapist whose humorous works are bound to make anyone feel better.

Well-made as well as witty, Tulin's work consists chiefly of lolling female nudes, gracefully and not so gracefully disposed, with titles such as "Seascape," which turns out to be a bather in a two-piece swimsuit and sunglasses. Some works--such as "Morning Exercise"--verge on parody, as a woman raises her enormous derrie re into the air in an attempted shoulder stand.

Less anecdotal--and more winning as pure sculptural form--is a series of female figures, divided into three parts, with giant legs and tiny torsos, each element cast separately, and then arranged in place. A more abstract outgrowth of this series--legs only, made from rolled slabs of clay--also succeeds, thanks to the artist's special gift for capturing the telling posture. Tulin overreaches only in her "Wall Figures," which somehow fall flat, and lack the spirit of her other work.

Tulin's show continues through April 16.

Addison/Ripley is at 9 Hillyer Court, in the alley between the Phillips Collection and the Cosmos Club. Hours are Tuesdays through Saturdays, 11 to 5. Hannelore Baron's Collages

The big banner announcing Hannelore Baron's show at Robert Brown, 1005 New Hampshire Ave. NW, is very different in spirit from the intimately scaled, highly personal collages inside. Fashioned from bits of paper, torn cloth, restrained color and graffiti-like markings, they have the look of ancient walls or old parchment, all bearing fragments of now indecipherable messages from the past. At first encounter, they are all rather delicate and poetic.

But slowly, these cryptic messages from the artist's mind begin to reveal themselves. There are vestiges of words, such as "don't," vestiges of names, such as "Jacob," and numbers with many digits, written as if on the arms of Nazi concentration camp victims. Tiny pictographs suggesting bound figures become discernible within clusters of box-like forms, and the pretty pale pink wash begins to read as blood. Why is the cloth always striped and stained, like prison garb? It dawns that these are images about victims--of every sort.

Baron fled to the United States from Nazi Germany in 1941, obviously with some visual experience of Paul Klee. Klee's whimsical brand of calligraphy does much to give this work a lyrical touch--and a look that remains always undisturbing and unspecific, until you put it together in your mind. There is no humor here, but there's no dirge either. Rather, these collages are monuments to the artist's memory, and--if we have it within us--to our collective memory as well.

The show continues through April 7. Hours are noon to 5, Wednesdays through Saturdays.