1. Mix the coriander, cumin, paprika, cayenne, allspice 1/8 teaspoon salt in a small bowl. Place the shrimp in a large bowl, add the spice mixture and toss to coat. Cover the plastic wrap and refrigerate 30 minutes.
2. In a large bowl, combine the spinach, oil and remaining salt. Divide spinach and shrimp evenly among four 15 by 12 inch sheets of heavy duty aluminum foil. Bring the edges of each sheet together and fold tightly to seal.
3. Heat the grill to medium high. Place packets on grill and close the cover; cook until spinach is wilted and shrimp is opaque, 5-7 minutes. Serve immediately.