In Vol. XXV., p. 253, I gave some account of the dimorphism of P. Bairdii, mainly from the observations and experiments of Mr. David Bruce. From what he had seen at Glenwood Springs, Coloradom he had satisfied himself that not only Bairdii and Oregonia were one species, but that P. Hollandii, Edw., formed part of the same. Though the two first named differ in facies more decidedly that do Turnus and Rutulus, and Rutulus and either Eurymedon or Daunus. Hollandii looks on the upper side like Bairdii, but beneath, while in general like Bairdii, the yellow spots are larger, making the surface much gayer.