Plate XXII. Whilst recording the evidences of the warm-blooded Vertebrates which have been found in the London Clay, I take the opportunity of describing some fossils from the same formation, referable to an order of reptiles which appears to have been very sparingly represented in the fauna of former periods of the history of the earth. Vertebrae joined enarthrodially by a deep anterior transversely oblong cup and a corresponding prominent posterior ball, and further articulated by two projecting posterior flat oblique processes wedged like the carpenter’s tenon into a mortice excavated in the anterior oblique processes of the succeeding vertebra; supporting, moreover, on either side of the fore-part of the body, an oblong convexity for the moveable articulation of the rib, belong unequivocally to a reptile of the Ophidian order. A group of about thirty vertebrae of this description, with a number of long and slender ribs, having expanded concave vertebral extremities, cemented irregularly together by a mass of indurated clay, forms part of the choice collection of fossils left by John Hunter, and now in the Museum of the Royal College of Surgeons, London*. A portion of the spinal column of apparently the same species of Serpent, measuring eighteen inches in length, and including twenty-eight vertebrae; a smaller group of seven vertebrae, and a few detached ones, are contained in the museum of Mr. Bowerbank. All these specimens are from the Isle of Sheppey. The vertebrae in each specimen present the same conformation and nearly the same size: they