A HISTORY OF DERBYSHIRE shark and its allies (Cestraciontidce) . Certain teeth of this type from Ticknall have been described as Venustodus serratus. Two species, Acrolepis hopkinsi and A. ivi/soni, of a Carboniferous genus of ganoid fishes have been described upon the evidence of scales from the county. Of the former species, which is from the Mountain Limestone, and is also known from other localities, the type specimens are in the Cambridge Museum. Of the latter, which is peculiar to the county, the types (now in the British Museum) were obtained from the Yoredale Rocks of Turnditch near Helper. A splenial bone from the Mountain Limestone of the county preserved in the Woodwardian Museum, Cambridge, was described by McCoy in 1848 as Cbeirodus pes-rance. It indicates a member of the ganoid family Platysomatidce, but is insufficient for accurate diagnosis. The fishes of the Derbyshire Coal Measures belong, with one excep- tion, to the ganoid or hard-scaled group. The exception in question is Sphenacanthus hybodoides, a widely-spread species of a numerously repre- sented Carboniferous genus. Of the Coal-Measure ganoids the first is Rhizodopsis sauroides, remains of which have been obtained from the Dalemoor Rake Ironstone of Stanton-by-Dale. This widely distributed species is a member of a large genus belonging to a family (Rhizontidce) characterized by the complicated internal structure of the teeth, which in this respect correspond to those of the primitive salamanders, or labyrinthodonts. Another family (Osteolepididtz) of fringe-finned ganoids is represented by two widely-ranging species, Megalichthys hibberti and M. pygmceus, of a well-known genus restricted 'to the Coal Measures and Calciferous Sandstone. The Ironstone of Stanton has also yielded remains of Ccelacanthus e/egans, a member of the type genus of an allied family of the same great group of ganoids. Peculiar to the Dalemoor Rake Ironstone of Stanton-by-Dale is the fish known as Platysomus tenui- sfriatus, a representative of the typical genus of a family belonging to a totally different group of ganoids, in which the fins have a rayed and not a fringed structure. The type of this species is a whole fish in the Museum of Practical Geology, Jermyn Street. Since the above was written Professor W. B. Dawkins exhibited before the Geological Society of London (Jan. 7, 1903) a number of molar teeth of Mastodon arvernensis from a cave at Doveholes, Buxton. This mastodon is a Pliocene species, occurring in the Norwich and Red Crags of England, and in the Upper and Lower Pliocene of the continent. Its remains have never previously been found in a cave, neither, I believe, is any other instance known of a cavern containing fossils of Pliocene age.
