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Show *722 PROF. T. W. BRIDGE ON THE [June 15, which had shown many small tubercular ulcers. The spleen and lungs, and especially the glands of the mesentery, were also infected. Mr. Oldfield Thomas, F.Z.S., gave an account of the Mammals obtained by Mr. John Whitehead during his recent expedition to the Philippines, and read some field-notes upon them by the collector. This memoir will be printed in the Society's ' Transactions.' The following papers were read :- 1. On the Presence of Ribs in Polyodon (Spatularla) folium. By Prof. T. W . BRIDGE, D.SC, F.Z.S. [Received May 21, 1897.] The ordinary text-book and other references to the presence or absence of costal elements in the skeleton of this Chondrostean Ganoid leave much to be desired on the score of precision, and not infrequently are diametrically opposed one to another on matters of fact. Thus, for example, in that excellent store-house of zootomical knowledge, the'Handbuch der Anatomie der Wirbelthiere'of Stannius (Aufl. 2, 1854, " Die Fische") there occurs the following passage :-" In den wesentlichsten Verhaltnissen zeigt Spaiularia sich iibereinstimmend mit Accipenser; nur fehlen die Eippen, oder werden vielmehr durch ligamentb'se Strange vertreten, die an der Basis knorpelige Elemente enthalten " (p. 21). Subsequently, in a footnote (p. 31) it is stated, "Harte Eippen fehlen hei Spatularla., J O n the other hand, Giinther (' The Study of Fishes,' 1880), in referring to the skeleton of the Ganoids, remarks:-" Eibs are present in most, but replaced by ligaments in Polyodon " (p. 75). Again, Wiedersheim, in his ' Comparative Anatomy of Vertebrates ' (English translation by Newton Parker, 1886), says, " The ribs of fishes show a very primitive condition usually extending along the whole length of the vertebral column (Lophobranchii, Spatularla)" (I. c. p. 48). In the same work a figure representing a lateral view of a portion of the vertebral column of Polyodon is given (Z. c. fig. 21, p. 35), but no costal elements are indicated. The same author, in his larger treatise, ' Lehrbuch der vergleichenden Anatomie der Wirbelthiere' (1886), referring to the same point, remarks :-" Bei Knochenfischen, z. B. bei Lophobranchiern, sowie auch bei Ganoiden (Spatularla), konnen die Eippen vollstandig fehlen " (I. c. p. 80). Finally, Vogt and Yung, in their ' Lehrbuch der praktischen vergleichenden Anatomie' (1889-94), refer to the absence of ribs in Chlmcera, many Eays, the Lophobranchii, and Spatularla (Bd. ii. p. 534). |