The traffic-congested, gritty blocks below the Port Authority on Ninth Avenue harbor more than a few dining treasures. Osteria Gelsi, opened in November by worldly chef Donato Deserio (Sign of the Dove, Il Cortile, Viareggio, Sette), attempts to be the latest. The semi-casual restaurant serves Puglian cuisine from the heel of Italy; Puglian specialties include pasta, along with a bountiful variety of produce and marine life. Osteria Gelsi has these, but the extraordinary olive oils and wines of Puglia are not prominent: the restaurant’s ostensible focus is the simpler cuisine of the region.

Indeed, the restaurant is at its best when it sticks to that rustic mode and its interesting, subtle dishes, but often it compromises, substituting a generic theatre-district Italian experience where a more distinctive one would be welcome. The over-lit, characterless interior is a symptom of this: threaded wall hangings and ornate, atavistic yellow awnings above doors suit the atmosphere poorly and offer little comfort. The white-clothed tables have the multifarious trappings of fine dining, but are almost too small to handle them: laden with a candle, flowers, Colavita-brand oil and vinegar cruets, flatware, water glasses, wine glasses, bread plates, and bread basket, they can barely accommodate dinner plates, and woe to the party that orders a side dish. Occasional sirens and honks from the avenue punctuate the meal. Servers are genial but often seem inexperienced, and a language barrier can create mutual confusion.

The ungraceful divide between rustic and rigorous extends to the menu, where delicious regional dishes are interspersed with decent run-of-the-mill fare. A few starters – such as grilled octopus bruschetta ($8.95) and a lemony, Romanesque chicory salad ($6.50) – have an unselfconscious charm, but too many feel like tacked-on crowd-pleasers. Small, bready crab cakes ($8.50), served with corn kernels and peppery mayonnaise, are barely Italian and completely forgettable, and a simple salad of spinach, sliced button mushrooms, and dry, brittle bacon ($5.95) looks and tastes like a refugee from a steakhouse. Generous slices of raw tuna carpaccio ($8.95) have a cracked-pepper crust and a salty, quasi-Asian dipping sauce of ginger and hot mustard, as well as an accompanying dollop of tapenade; despite its questionable provenance, this dish is tasty.

But it’s only after the starters that the restaurant begins to impress, specifically with a host of lively, idiosyncratic pasta dishes. These can be ordered as an intermediate course, singly or shared, or, better, as an end in themselves. Conchiglie e cavolfiori – miniature pasta shells with cauliflower ($11.50) – belies its unassuming name with brisk salty tart flavors. Long shreds of crumbly, rich ricotta salata cheese top crisp-fried capers that burst between the teeth; the dish emits the mild flowery perfume of sweet red onion. Another unusual treat is creamy-textured wide pappardelle ($12.95), whose supple folds swathe a clutch of warm berries: mulberries, blueberries, and juicy wild cherries. Blueberry grappa and fresh mint subtly sweeten the pasta; pine nuts and aged cheese give it a harmonious savory balance.

A dramatic timballo ($12) layers round, toothsome sheets of pasta with a formidably hearty meat ragu and a sparing dose of rich bechamel sauce. The almost-too-salty ragu has the concentrated, mature taste of long cooking; it also enriches a dish of strascinati ($12.50), absorbent, chewy pasta shapes that the menu, incontestably, calls “earlobe-shaped.” Another enticing pasta, tossed with fresh sea urchin roe and artichoke hearts, depends on the whims of the market and wasn’t available on my visits.

The restaurant’s plain, almost Spartan meat and fish offerings show none of the pastas’ appealing subtlety. They’re inoffensive, but little more: the sort of simple, unadorned preparation that allows superior ingredients to shine, or, in this case, lets inferior ones wither in the spotlight. If this course can’t be avoided altogether, savory side dishes, including a startlingly, stimulatingly bitter chicory-laced fava-bean puree ($5.50), give it a welcome pillar of flavor. Lamb chops ($18.50) are grilled and served over green beans and roasted potatoes; the meat is just shy of tender and moderate in flavor. A filet of scorfano ($16.50), also known as scorpion fish, receives a gentle roasting treatment with white wine that maximizes the textural effect of its very delicate flesh, but adds little flavor to a fish that already has little of its own. Beautiful and inviting grill marks are misleading on a less than perfect, negligibly seasoned piece of sea bream ($16.50); roasted garlic and bay leaves garnish the plate but shirk where they are needed most.

Desserts, which stick to the Italian-restaurant basics, are decidedly not a specialty: tiramisu ($5.95) tastes bland and watery, and ricotta cheesecake ($5.95) is dryish and neither tart nor sweet enough.

Wines range from Beringer’s white zin at $21 to a huge Raimondi amarone at $95. The majority of the list falls under $40 or even under $30, including the balanced Sicilian blend Nuhar ($23), a dense, modern primitivo di Manduria ($29), and a rich, aromatic Greco di Tufo ($30) that gives the fish something to lean on.

There’s no doubt about Mr. Deserio’s ability, which he has proven at so many New York restaurants (and in the exceptional pastas here), which causes one to wonder why Osteria Gelsi is such a watered-down version of what it could be. Perhaps the young restaurant will learn to concentrate on its strengths; until then, go for the timballo.

Osteria Gelsi, 507 Ninth Ave., 212-244-0088.