On our Plate is depicted the head-shield of the well-known Old Red Sandstone fish, Cephalaspis, the genus first described by Agassiz in 1835, the species C. Salweyi, by Egerton in 1857, and still later as C. asterolepis, by Harley in 1859. The specimen was obtained by Mr. John Edward Lee, F.G.S., of Torquay, from the “Cornstones,” Old Red Sandstone, Skerrid Vawr, near Abergavenny, and is drawn about one-third less than the natural size. “ Two cornua were obtained by Dr. Mac Cullough from the same quarry at Abergavenny, furnishing the evidence of these parts which are wanting in Mr. Lee's specimen” (Lankester).