The specimen (No. 37,958 of the British Museum Collection), which forms the subject of the present notice, is from the Blackband Ironstone of Airdrie, and, I understand, from the same bed which yielded the first known specimen of Anthracosaurus Russelli. The fossil is unfortunately very imperfect, though it displays a considerable portion of the body of a large fish lying on its right side. Both the head and the caudal extremity, however, are gone, nor is the ventral margin shown; but the line of the back is pretty nearly intact, and is seen to be bordered by the long dorsal fin characteristic of Phaneropleuron and of Uronemus. What remains of the body shows a confused mass of ribs, spinous processes, and inter-spinous ossicles, compressed against a groundwork of what are apparently large and very thin rounded scales. The specimen, measuring 15½ inches in length, by 5½ inches in breadth at its broadest part, presents thus a considerable part of the abdominal, with the anterior part of the caudal region of a fish, which, when entire, must have been in all probability more than two feet long.