Of the ANIMAL REMAINS of fishes belonging to the gray sandstone, the Cephalaspis Lyellii was one of the earliest discovered, as it still constitutes one of the most remarkable of these fossil relics. The head of this creature, and hence the name buckler-headed, is large in proportion to the body, forming nearly one-third of its length. The outline is rounded in the form of a crescent, the lateral horns inclining slightly toward each other, while the anterior or central parts project considerably outward; this peculiarity of structure is occasioned by the intimate anchylosis of all the plates which compose the cranium. The body resembles in appearance an elongated spindle, swelling out on the ridge of the back, and narrowing to the extremity of the tail, which terminates in a long slender point. How like, peradventure, the very dagger with which the murderous Thane of Glammis threatened to render— “The multitudinous seas incarnadine, Making the green one red!” The sanguineous fluid, in those days, was not indeed very plentiful; but the sharp-horned orthoceræ, and the swift predaceous nautili were cotemporaries; and hence, either for protection or attack, we find that, while the head of the Cephalaspis was one entire plate of enameled bone in the upper division, the body was wrapped in a closely woven net-work of bony scales, of peculiar form, and differing from the scales of every other genus of ganoids. The scales along the center of the sides are so high, that their breadth exceeds their length eight or ten times, occupying more than half the height of the animal. Everywhere meshed in smaller but equally impervious nettings, there are of the larger scales, from twenty-six to thirty covering the sides, thereby completing a mail-clad figure of a singularly warlike aspect, and bidding defiance, like his great anti-type, to all his foes,—“let fall thy blade on vulnerable CRESTS”—but now, like Banquo’s ghost, “the bones are marrowless.”