PALAEOSPONDYLUS  , a small

fish-like organism, of which the skeleton is found fossil in the Middle Old Red Sandstone From British Museum Guide to Fossil Reptiles and Fishes, by permission of the Trustees . Palaeospondylus gunni, restored by Dr R . H . Traquair . (Nearly twice nat. size.) of Achanarras, near Thurso, Caithness . It was thus named (Gr. ancient vertebra) by Dr R . H . Traquair in 189o, in allusion to its well-developed vertebral rings; and its structure was studied in detail in 1903 by Professor and Miss Sollas, who succeeded in making enlarged models of the fossil in wax . The skeleton as preserved is carbonized, and indicates an eel-shaped animal from 3 to 5 cm., in length . The skull, which must have consisted of hardened cartilage, exhibits pairs of nasal and auditory capsules, with a gill-apparatus below its hinder part, but no indications of ordinary jaws . The anterior opening of the brain-case is surrounded by a ring of hard cirri . A pair of " post-branchial plates " projects backwards from the head .

The vertebral

axis shows a series of broad rings, with distinct neural arches, but no ribs . Towards the end of the body both neural and haemal arches are continued into forked radial cartilages, which support a median fin . There are no traces either of paired fins or of dermal armour . The affinities of Palaeospondylus are doubtful, but it is probably related to the contemporaneous armoured Ostracoderms .