The disk is very broad, in consequence of the great development of the pectoral fins, which, however, leave the sides of the head free, and reappear at the extremity of the snout as a pair of detached (cephalic) fins. Viviparous.
“Devil-fishes,” “Sea-devils,” or “Eagle-rays.” Generally of large size, inhabiting temperate and tropical seas. Some genera possess a pair of singular cephalic processes, which generally project in a direction parallel to the longitudinal axis of the body, but are said to be flexible in the living fish, and used for scooping food from the bottom and conveying it to the mouth. In all the species the dentition consists of perfectly flat molars, forming a kind of mosaic pavement in both the upper and lower jaws: a most perfect mechanical arrangement for crushing alimentary substances.
Fig. 129.—Jaws of an Eagle-Ray, Myliobatis aquila.
Myliobatis.—Teeth sexangular, large, flat, tessellated, those in the middle much broader than long; several narrower series on each side. Tail very long and thin, with a dorsal fin near its root; generally a serrated spine behind the fin.
Seven species are known, two of which are European, one (M. aquila) being almost cosmopolitan, and occasionally found on the British coast. The young differ much from the adult, having no median series of larger teeth, but all the teeth of equal size and regularly sexangular. Also the tail is much longer in young examples than in old ones, and the coloration more ornamental. Teeth of species very closely allied to, or perhaps even identical with, existing species, are found in tertiary formations.
Aëtobatis.—Form of the head, body, and tail as Myliobatis. The nasal valves remain separate, each forming a long flap. The lower dental lamina projects beyond the upper. Teeth flat, broad, forming a single series, equivalent to the median series of Myliobatis, there being no small lateral teeth.
Fig. 130.—Aëtobatis narinari.
One species only (A. narinari) which is found in almost all tropical seas, and of exceedingly common occurrence in the Atlantic and Indian Oceans; it does not seem to grow to a very large size (perhaps not exceeding 5 feet in width), and is readily recognised by numerous round bluish-white spots, with which the back is ornamented. Fossils of this genus occur in the English Eocenes and the Swiss Molasse.