[528] Proc. Geol. Soc. vol. ii. p. 687.
[529] Two teeth are figured in Dixon’s Fossils of Sussex, pl. xii.; the specimens are in the British Museum; see Petrifactions, p. 414.
Fossil Rays.—The teeth of these fishes are characterised by the extraordinary transversal development of the median teeth in both jaws. Instead of pointed teeth, they have wide, flat, tesselated dentary plates in each jaw, composed of distinct pieces, juxtaposed and connected by their margins, and united by fine sutures. In some species the teeth are equal, in others of various sizes; they present numerous modifications of arrangement, and are always disposed in symmetrical rows. In the genus Myliobatis (Eagle-ray) the teeth of the median row are of an extraordinary width, while their length does not exceed that of the lateral plates, or chevrons, which are of an irregular hexagonal form, and disposed in two or three rows on each side. There are five living species of Myliobatis, and eighteen fossil species have been found in the Tertiary strata at the Isle of Sheppey, Hordwell Cliff, and Bracklesham Bay. I have figured a specimen of part of the upper jaw of a species (M. micropleurus, [Lign. 194], fig. 2), in which the median teeth are very wide, and have two lateral rows of small, irregularly hexagonal, plates. The surface of the teeth in this species is smooth; but in others it is striated longitudinally (Bd. pl. xxvid. fig. 14). In an allied genus, Ætobatis, from the Tertiary beds at Bracklesham, the lower jaw projects beyond the upper, and in each there is a row of flat, transverse teeth, without lateral plates.
Lign. 194. Fossil Teeth of Fishes
| Fig. | 1.— | Ceratodus emarginatus: 1/2 nat. Lias Bone-bed. Aust Cliff. A single dental plate. |
| 2.— | Myliobatis micropleurus: 1/3 nat. Tert. Isle of Sheppey. A series of six median teeth, with the corresponding lateral teeth. | |
| 3.— | Pycnodus Mantelli. Weald. Tilgate Forest. This specimen consists of the vomerine bone, with a median row of flat, arched teeth, and two rows on each side of elliptical teeth, arranged alternately. |
To this notice of the fossil Rays, we may add, that a gigantic Torpedo has been discovered in that celebrated locality of Ichthyolites, Monte Bolca: and that Sir Philip Egerton has recently enriched his matchless collection of fossil fishes, by a perfect Ray, from Mount Lebanon. It is figured and described in the Quarterly Geol. Journ. vol. i. pl. v. p. 225, under the name of Cyclobatis oligodactylus. It is a small species, resembling the common Rays in its general appearance, but is surrounded by a broad, flexible, cartilagino-membranous fin; the skin is smooth, the teeth and eyes are small, the tail is slender; there are no traces of dermal spines, tubercles, or defensive weapons. In many points of structure it resembles the Torpedo; and may possibly, like that fish, have possessed an electric organ. It is 31/2 inches long, and 3 inches wide across the expanded fins.