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Show 1904.] OSTEOLOGY OF THE ELOPID.E AND ALBULIDAE. 73 the Teleostean series (excluding extinct forms sucli as the Pholi-dophoridye, in which " it is not yet quite clear that the mandible was destitute of splenial and coronoid elements" (Smith Woodward, Vert. Palseontol. 1898, p. 114), might more than any others be expected to possess traces of this constituent. The size and shape of the dentary bone vary very considerably. The bone is usually large; but it is much reduced, especially in its anterior parts, in Chanos. The coronoid process is usually formed entirely by the dentary, but the ectosteal articular occasionally forms the hinder part of it. In Chatoessus the process is situated unusually far forward, in a position recalling that of the remarkable coronoid process of Gonorhynchus. In the extinct family Sa-urodontidse the teeth are lodged in sockets; and Boulenger, in his recent synopsis of the families of Teleostean fishes (Ann. & Mag. Nat. Hist. xiii. 1904, p. 164), places the Chirocentridse next the Saurodontidte, and separates them from the Clupeidse because they have " teeth in sockets." The teeth of the three specimens of Chirocentrus dorab examined for the purposes of this investigation are, however, certainly not lodged in sockets; they are ancliylosed to the edge of the bone, and are flanked by a slight ledge on the external side, exactly as in Coilia, for instance. Hyopalatine Series.-The presence of one or two articular heads for the front of the hyopalatine arch, a matter upon which Swin-nerton (Quart. Journ. Micro. Sci. xlv. 4, 1902, pp. 551, 556-557, <fe 584) lays considerable stress, may possibly be an adaptive feature related to the length of the ethmoid region of the skull, for in Elops and Megalops the ethmoid region is short, and the front of the hyopalatine arch has but a single head, whereas in Albula the ethmoid region is long and there are two heads to the palatine. The difference does not strike one at the outset as likely to be of fundamental importance: extended investigations upon dissected, i. e. not dried, skulls alone can decide the point. An unusual condition occurs in Coilia, in which the ethmoid region of the cranium is short and the palatine has two heads; but these are right and left, and not anterior and posterior. This peculiarity is not shared by the allied genus Engraulis. The palatine bone is fused with the ectopterygoid in Arapaima, Osteoglossum, and Notopterus, and in these genera and in Hyodon there appears to be no endosteal part of the palatine. In the Mormyroid fishes there is no separate entopterygoid, and the palatine bone is fused with the side of the vomer. The metapterygoid attains its maximum size relatively to the adjacent bones in Coilia; in Gonorhynchus the other extreme is reached, for here it is reduced to a fine needle of bone. The articulation between the metapterygoid and entopterygoid region of the hyopalatine arch of Osteoglossum and the lateral process of the parasphenoid described by Bridge in 1895 (Proc. Zool. Soc. 1895) is considered by Swinnerton (I. c. p. 572) on ernbryological |