The original fossil, from which the cast was taken, is in the New York Museum. I am indebted to Mr. Rubens Peale, the liberal proprietor of that flourishing and important institution, not only for the use of it in this Monograph, but also for some valuable information relating to other species. The precise locality of Mr. Peale's specimen is not known, but in the cabinet of J. P. Wetherill, Esq., there is a fine head of the C. diops which was found in the State of Ohio. Both specimens are mineralized by the same kind of soft grey coloured limestone--and I have but little doubt that they were derived from the same place. Calymene Macrophthalma.[20] _Brongniart._ Cast No. 9. [Footnote 20: From the Greek for "Great eyes."] Clypeo antice, caudaque postice attenuatis, oculis magnis exsertis. This species, according to Al. Brongniart, who first described it, is remarkable for the magnitude and protuberance of its eye-shaped tubercles, and by the prolongation of the anterior portion of the buckler, in the form of a snout. The back is marked by 12 or 13 articulations, which are thicker than those of the tail. The tail is short, pointed, and without expansion. The middle lobe, or front of the _buckler_, in this calymene, is said by Brongniart to be marked on its sides by three oblique plicæ or wrinkles, but we have not been able to discover this character in any of the specimens to which we have access; neither do they exhibit any remarkable prolongation in the anterior portion of the _buckler_, as stated in his specific character. The specimens which we have examined, agree pretty well with the representation he has given of the C. Macrophthalma, Plate I. fig. 5. A. B. & C. made from a drawing by Mr. Stokes, from a fossil found in Coalbrookdale (Eng.). This trilobite is common in several parts of the United States. According to Dr. J. E. Dekay,[21] the C. Macrophthalma is found on the Helderberg mountains, near Albany, and at Coshung creek, not far from Seneca lake, in the State of New York. It occurs also at Leheighton, in Pennsylvania--at the Falls of the Ohio, and at several other localities. We have examined a number of specimens of the C. Macrophthalma, contained in the rich cabinet of fossils, in the Academy of Natural Sciences, and have never seen any individual which resembles the fig. 4, Plate I. of Brongniart; and in no instance is the front of the buckler marked by three oblique folds, a character stated as peculiar to this species. The C. Macrophthalma, (variety) occurs in large quantities in Leheighton in Pennsylvania, and we are indebted to Mr. D. Keim, for some fine specimens from that locality. [Footnote 21: See Annals of Lyceum, Vol. I. p. 188.]