How to Make It
Bring 1 quart of water to a boil in a medium saucepan over high heat. Add lime rinds to the boiling water. Add the frozen shrimp and salt, and let the water return just to a boil. Remove from heat; cover and let stand 5 minutes. Drain and discard lime rinds. Rinse shrimp with cold water, and remove tails.
In a large bowl, combine lime juice, jicama, cilantro, scallions, jalapeño, and garlic. Add shrimp and black pepper. Let stand 10 minutes at room temperature, or refrigerate up to 4 hours until ready to serve.
Line 4 plates with romaine lettuce leaves. Divide the salad among the plates and serve.