In making some excavations on the Pacific Railroad, near St. Louis, the workmen came upon some flint nodules of a curious shape.— They are rounded much like a melon, and may easily be supposed to be a petrification ofthat fruit. A specimen having been broken with a tolerably smooth cleavage, disclosed a series-of what appeared to be rings, arid in th* cgntre the appearances of some ore looking like silver ore. From one of them in its natural state a portion of what might be mistaken for an outer coat had been removed, much as if the stone had once been a melon and been petrified after a part of its rind had been peeled away. The surfaces of these nodules exhibited numerous perfect impressions made by the leaves of plants, so distinctly and so delicately traced as to produce a very beautiful effect. The specimens were found in a ledge of limestone, which abounds in stones of a similar kind.