Coarsely chop bones and trimmings; place in a bowl. Cover with water and let stand 30 minutes. put clams in a second bowl and cover with water; add cornmeal and let stand 30 minutes. Remove clams from bowl; rinse in a colander. Drain and transfer bones and  trimmings to a clean bowl.

In a large Dutch oven or wide heavy pot, heat 3 tablespoons oil over medium-high heat; add celery, carrot and onion. Reduce heat to medium and cook, stirring occasionally, 8 minutes, then stir in bones and trimmings, and cook 5 minutes more.  

Add wine and bring to a gentle simmer; simmer 20 minutes. 

Remove pot from heat. Remove and discard large fish bones. In batches, pass remaining pan contents through food mill into a large bowl, discarding solids as you go. Strain milled broth through a fine-mesh sieve (you should have about 4 1/2 cups broth). Transfer broth to a pot and bring to a simmer over low heat; remove from heat and cover to keep warm.

Bring a large pot of salted water to a boil. Meanwhile, in a large high-sided skillet, heat remaining 4 tablespoons oil over medium-low heat. Add parsley, garlic, rosemary and chile; cook, stirring occasionally, 3 minutes. Add clams, increase heat to high and toss to coat with oil. Reduce heat to medium, cover and cook until clams open, about 8 minutes (discard any that do not open); remove from heat.

Cook pasta in the boiling water until al dente. Meanwhile, gently reheat broth.

Drain pasta, then add to pan with clams; toss over high heat to combine. Divide pasta and clams among serving bowls. Ladle hot broth over the top. Serve immediately.