Mix 1½ c. sugar, ½ c. flour and 1 tsp. salt; combine with blueberries and lemon juice. Pour into a greased 13 X 9 X 2" (3-qt.) baking pan; dot with butter.
Place in a preheated hot oven (400°) about 15 minutes; be sure that mixture is hot and bubbling.
In the meantime, mix the topping. Sift together 2 c. flour, baking powder, 2 tblsp. sugar and 1 tsp. salt. Cut in shortening until mixture resembles coarse meal. Add milk and slightly beaten egg to dry ingredients. Stir with fork to blend well.
Remove hot blueberry mixture from oven. Drop topping mixture onto hot blueberries, making 12 biscuits. Return to hot oven (400°); bake about 20 minutes, or until biscuits are browned.