Conventional wisdom would have us believe that the dog days of summer find their analogue on the walls of Newbury Street galleries. Yet for every show bent to the tourist trade (where’s the ocean the rest of the year?) or designed to allow for a staff’s vacation (those group exhibits whose organizing principle is that the work all hails from the same flat file in a nearby back room), another, bigger truth obtains.

Summer is also the time of year when galleries take chances, and a look at any number of venues reveals first-time appearances by both promising new artists and established artists never before seen in Boston. And since summer exhibits tend to be group shows, this is also the season to sample work by talented artists who typically must wait years between solo or two-person exhibits.

Nowhere are the riches more concentrated than on the third floor at 14 Newbury Street, where several galleries are showing fine work. Almost brand new at Miller Block (their initial appearance, in another group show, ended earlier this month) are the playful, enigmatic, bright abstractions by Henry Samelson that seem part landscape, part cartoon, and part surgical procedure. Samelson paints with enamel on small (14x7) aluminum rectangles, and their uniform diminutive size combines with their large number to make me think of playing cards: I can imagine shuffling and dealing them. Yet it’s in the context of his near-buffoonery that Samelson establishes his seriousness. Small arches, like unevenly sized croquet hoops, stitch the upper half of one work, and they seem to be emerging from sizable black holes on the surface of a floating planet. Yet without any reference points, it’s impossible to figure out the scale. Are we looking at a close-up or an aerial view? Are those black holes moles or craters?

Samelson plays with such ambiguity in a pared-down language of simple forms, and his aim appears nothing less than to reinvent the sensual world. Flesh becomes landscape, silly becomes tense, awkward becomes dramatic. Below the crimson arches, with their suggestion of sutures and hair plugs, white disks hover in a dark blue space. They’re too big to be stars, but they’re also too luminous to dispel the idea of stars.

Nowhere are the riches more concentrated than on the third floor at 14 Newbury Street, where several galleries are showing fine work. Almost brand new at Miller Block (their initial appearance, in another group show, ended earlier this month) are the playful, enigmatic, bright abstractions by Henry Samelson that seem part landscape, part cartoon, and part surgical procedure. Samelson paints with enamel on small (14x7) aluminum rectangles, and their uniform diminutive size combines with their large number to make me think of playing cards: I can imagine shuffling and dealing them. Yet it’s in the context of his near-buffoonery that Samelson establishes his seriousness. Small arches, like unevenly sized croquet hoops, stitch the lower half of one work, and they look as if they attached to the surface through sizable black holes in the ground. Yet without any reference points, it’s impossible to figure out the scale. Are we looking at a close-up or an aerial view? Are those black holes moles or craters?

Samelson plays with such ambiguity in a pared-down language of simple forms, and his aim appears nothing less than to reinvent the sensual world. Flesh becomes landscape, silly becomes tense, awkward becomes dramatic. Above the crimson arches, with their suggestion of sutures and hair plugs, white disks hover in a dark blue sky. They’re too big to be stars, but they’re also too luminous to dispel the idea of stars.

The Miller Block Gallery has a couple more first-timers. Delicate, austere stretches of graphite, Whitney River’s two drawings of leafless willow branches enjoy a cool clarity. Even as the larger art world embraces the big, the busy, and the bombastic, she breathes fresh air. The willow branches stand against no other backdrop than the whiteness of the paper on which they’re drawn. You can almost feel a breeze.

Joe Kievitt is interested in the patterned tile work of leaves in a tree, and whereas River’s perspective is frontal and eye-level, he seems to be looking at his arboreal confections from below. To see his drawings is to feel the canopy effect of a forest in our own climate zone, where the foliage, unlike that of the tropics, seems in a hurry. At the same time, Kievitt’s leaves read as highly stylized. Crisp-edged and interlocking, they could be mosaics in the floor of a church or mosque.

FIVE OF THE 12 PHOTOGRAPHERS on view in " Embody: Inference in Figurative Photography, " the exquisite show at Howard Yezerski Gallery, are veteran artists, some internationally acclaimed, whose work has gone largely (or entirely) unseen here. Significant among them is the Chilean-born, Hungarian-raised, and now London-based photographer Mari Mahr. Her Boston debut, 13 Clues to a Fictitious Crime, will mark one of the year’s highlights. If René Magritte were a photographer, he’d have done work like Mahr’s, whose formalism combines with domestic outrageousness to create intense, surreal imagery.

As is the case with Magritte, what’s most memorable about Mahr’s photographs are the subtle dislocations that grow more dramatic the longer you look: the wing of a bird that dwarfs a city; the dead fish lined up parallel to a fork and knife in a place setting; an empty picture frame obscuring a photo of the face of a woman. Despite the implied but ever-elusive narrative elements of 13 Clues and despite the series’s reliance on old-fashioned, European-looking objects — the worn paint on a doll’s china face, the recurrent pocket watch — nothing feels hoky or strained. Mahr writes of this work that the " recurring face is that of my mother. . . . The objects also come from my family — I brought them all with me from Hungary. " That could be one reason these photographs matter, but there’s also the artist’s sharp compositional sense, and the way she depicts the real and the make-believe simultaneously. An actual dove’s wing is superimposed on an antiquated, aerial photograph of a city’s rooftops; the result is an immediate, resonant distortion of time. When Mahr’s camera clicks, multiple moments in time come together — here it’s a once-living bird and a dated snapshot.

If Mahr’s images are haunted by the past, Boston artist John Goodman’s photos are haunted by the present. Looking at his one contribution to " Embody " — two abstracted figures framed in black, silhouetted yet blurry — gives you no hint of the remarkable project from which it is excerpted. The Times Square Gym is a gritty, passionate series of black-and-white photos of the middle-aged trainers and the young boxers they coach in a dilapidated space in what until recently had been this country’s pre-eminently seedy neighborhood. Published as a book in 1996, it represents that rarest of artistic achievements: a monumental homage to the lower working class. Its poignancy owes to its unflinching lack of sentimentality.

Knowing the context whence Goodman’s photo issues makes it easy to wish for more of his work in the show, particularly since the vast majority of his images are marked not by abstraction but by their fleeting figurativeness. (Even his posed stills have momentum.) I was grateful to be introduced to his enormous talent.

A GROUP SHOW OF SCULPTURE at Judy Ann Goldman Fine Art brings work from a newcomer and an insufficiently seen veteran to view. Siobhan Liddell encases sheets of paper in plexiglass boxes, and they’re amazing. You look down into her transparent packages, which are set on the floor and stand only about a foot high, to see what appears to be the throat of an oversized flower. Although the upper surface of each sheet is white, Liddell has created a reddish, uneven tunnel by painting their undersides, cutting out the middles, and then ingeniously stacking them an inch apart. Delicate yet voluminous, ethereal yet square, these are works of integrity and humor.

Also on view is a sampling of works from Jill Slosburg-Ackerman’s most recent series, Restless Shelves. Her interest is in combining organic, viscous, often out-of-control forms with staid, pedestrian, utilitarian objects. Each of her shelves is simply constructed and potentially useful — yet beneath each shelf something’s going on. In #5, the particle board appears to have escaped its veneer and come alive. It’s weirdly disturbing.

Unfortunately, the shelves are lined up high on the same wall and set tightly together. Not only does this arrangement call attention to their status as Art, it forgoes the opportunity to catch people off guard. How much more delightful had they been placed around the gallery for people to start to rest their drinks on.