Teeth and spines of all these genera are common as fossils from the Eocene onwards, as well as many of the extinct genus, Ptychodus, with cyclospondylous vertebræ. Ptychodus mammilaris, rugosus, and decurrens are characteristic of the Cretaceous of England. Myliobatis dixoni is common in the European Eocene, as is also Myliobatis toliapicus and Aëtobatis irregularis. Apocopodon seriacus is known from the Cretaceous of Brazil.
Fig. 349.—Eagle-ray, Aëtobatis narinari (Euphrasen). Cedar Keys, Fla.
Family Psammodontidæ.—The Psammodontidæ are known only from the teeth, large, flat, or rounded and finely dotted or roughened on the upper surface, as the name Psammodus (ψάμμος, sand; ὀδούς, tooth) would indicate. The way in which the jaws lie indicates that these teeth belonged to rays rather than sharks. Numerous species have been described, mostly from the Subcarboniferous limestones. Archæobatis gigas, perhaps, as its name would indicate, the primeval skate, is from the Subcarboniferous limestone of Greencastle, Indiana. Teeth of numerous species of Psammodus and Copodus are found in many rocks of Carboniferous age. Psammodus rugosus common in Carboniferous rocks of Europe.
Fig. 350.—Devil-ray or Sea-devil, Manta birostris (Walbaum). Florida.
Family Mobulidæ.—The sea-devils, Mobulidæ, are the mightiest of all the rays, characterized by the development of the anterior lobe of the pectorals as a pair of cephalic fins. These stand up like horns or cars on the upper part of the head. The teeth are small and flat, tubercular, and the whip-like tail is with or without spine. The species are few, little known, and inordinately large, reaching a width of more than twenty feet and a weight, according to Risso, of 1250 pounds. When harpooned it is said that they will drag a large boat with great swiftness. The manta, or sea-devil, of tropical America is Manta birostris. It is said to be much dreaded by the pearl-fishers, who fear that it will devour them "after enveloping them in its vast wings." It is not likely, however, that the manta devours anything larger than the pearl-oyster itself. Manta hamiltoni is a name given to a sea-devil of the Gulf of California. The European species Mobula edentula reaches a similarly enormous size, and Mobula hypostoma has been scantily described from Jamaica and Brazil. Mobula japonica occurs in Japan. A fœtus in my possession from a huge specimen taken at Misaki is nearly a foot across. In Mobula (Cephaloptera) there are teeth in both jaws, in Manta (Ceratoptera) in the lower jaw only. In Ceratobatis from Jamaica (C. robertsi) there are teeth in the upper jaw only. Otherwise the species of the three genera are much alike, and from their huge size are little known and rarely seen in collections. Of Mobulidæ no extinct species are known.
FOOTNOTES:
[150] Dr. Peter Schmidt has made a sketch of this little shark at night from a living example, using its own light.