. Carnegie Institution of Washington publication. . A. Upper jaw (Tab. D, fig. 2). B. Lower jaw (Tab. D, fig. i). Text-fig. 9.—Jaws of Myliohatis (Aetobatis) narinari, after Agassiz. It seems unbelievable that Agassiz should have allowed to slip into his work so great an error as the above transposition of the jaws, but he did so and he repeats it in the explanation of the plates. Where he says upper, we should read lower, and vice versa. He next goes into a microscopical examination of the tooth structure, into which we will not follow him here.^ This occurs on pp. 79 and 80 of the general in
. Carnegie Institution of Washington publication. . A. Upper jaw (Tab. D, fig. 2). B. Lower jaw (Tab. D, fig. i). Text-fig. 9.—Jaws of Myliohatis (Aetobatis) narinari, after Agassiz. It seems unbelievable that Agassiz should have allowed to slip into his work so great an error as the above transposition of the jaws, but he did so and he repeats it in the explanation of the plates. Where he says upper, we should read lower, and vice versa. He next goes into a microscopical examination of the tooth structure, into which we will not follow him here.^ This occurs on pp. 79 and 80 of the general introduction to his "Poissons Fossiles," volume iii. However, on pages 325-326 he gives the following illuminating description of the jaws and their functions. This genus (Aetobatis) is characterized by the form of the jaws, of which the lower projects in front, while the upper Is much shorter and Is squarely cut ofT. Both are fur- nished with a single row of transverse teeth without lateral chevrons. The lower jaw Is, as In the genus Myliobatis, longer than the upper jaw (tab. D, fig. i) [present text-fig. 9B]. The bone of this jaw Is longer than wide. The dental plate, whose surface Is almost flat in its whole extent, does not cover all the surface of the jaw. In return, its anterior part projects considerably over the jaw, and as the teeth are arched In front, this only makes the anterior edge more salient. Since all the teeth are parallel with each other, their surface offers the aspect of strips curved and joined, the one to the other. The last tooth alone is transversely cut oflf. The anterior part of the dental plate, which is lightly shaded In figure 2 of table D [present text-fig. 9A], is used for the rubbing of the two jaws against one another. The upper jaw Is much wider than long. The dental plate covers it unlike that of the lower jaw, In that the strips are almost straight and only a little bent at their edges, and thus they surround the anterior border
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