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Show 348 MR. A. SMITH WOODWARD ON N E W FISHES [Apr. 15, superior border exhibit a deep, narrow depression overlapped by supra-maxillary bones (smx.). Of the latter the hindermost is irregularly triangular, pointed behind, deepest in front, with a sharp re-entering angle on the anterior border, and a long antero-superior process ; the second element is also triangular, but much elongated, its narrow base fitting into the re-entering angle just mentioned, and its tapering apex directed forwards. In the mandible, the articular bone (ar.) is laterally compressed, abruptly truncated behind, narrow beneath the socket for the condyle, and much expanded forwards in the form of an elevated triangular plate. The dentary (d.) is long, thin and deep, abruptly truncated at the symphysis, but too much crushed to exhibit all the details of form. The mandibular suspen-sorium is somewhat inclined forwards, and the dentary symphysis evidently projects in advance of the premaxillae. Of cheek-plates and circumorbitals almost all traces are lost, but fragments of a thin lamina of bone, above and exterior to the metapterygoid, may probably be assigned to this category; they are marked by somewhat radiating ridges. Of the hyoid arch and its appendages, the right ceratohyal, with the distal end of the epihyal in position, is exhibited in the small Purbeck fossil described hy Agassiz, and there seems to be evidence of small, slender, widely spaced branchiostegal rays. The operculum and suboperculum are not distinctly recognizable in any specimen ; but the preoperculum (Plate X X I X . fig. 2) is a characteristic element. This bone is of considerable size, narrow and deep, with a broad, much thickened anterior border; its lower limb is relatively large, meeting the upper limb in a sharp angulation ; and the hinder expansion of the upper limb is almost smooth, while that of the lower limb is separated from this by a transverse ridge and is itself marked by three or four rounded, parallel, or somewhat divergent ridges. Dentition.--The oral margin of the maxilla is thickened, rounded, and regularly reticulated in such a manner as to suggest the original presence of a uniform cluster of very small teeth. None of these are preserved ; and the teeth of the mandible are also not shown, its dentigerous border being obscured by pyritous matrix and the overlap of the maxillae. In the small Purbeck fossil, however, the symphysial end of the right dentary is well exhibited (Plate XXIX. fig. 1). Here are preserved a few small, stout, conical teeth, which seem to have formed part of an irregular spaced series, around and between which were still more minute teeth. Branchial Arches.-In the postero-inferior region of the type specimen, a short vertical series of small, horizontally directed, thick rods is conspicuous (g.r.), though very imperfectly preserved; and the appearance of these fragments is at first suggestive of the base of a powerful pectoral fin. The supposed Lepidotus minor of Agassiz, however, explains that the structures in question are referable to the branchial apparatus ; and in the last-mentioned fossil one of the arches is tolerably well displayed from the outer aspect (Plate XXVIII. fig. 2). A most singular feature is thus made known, the arch being provided with a close series of enormous bony gill- |