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Show 230 DR. A. GUNTHER ON NEW AMERICAN FISHES. [Mar. 26, the nuchal carapace are rounded, reaching to the base of the second soft ray of the dorsal fin. Dorsal spine serrated in front and behind, the anterior denticulations being directed upwards. Pectoral spine very long, much longer than the head, extending to the ventral. Caudal peduncle shielded above and below. Uniform blackish; dorsal fin white, its middle black; base of the anal fin and the two posterior rays white. Three examples, 14 inches long, were sent by Hr. Kappler from Surinam. This fish swallows Ampullarias of a diameter of an inch, and, after having digested the animal, passes the shells, not broken or damaged in any way. The mouth is not larger than in the allied species. OXYDORAS ACIPENSERINUS. (Plate XX.) D. 1/6. A. 16. P. 1/10. V. 7. L. lat. 42. This fish is distinguished from all its congeners by the peculiar shape of the head and snout, which is elongate-triangular, pointed, and much depressed in its anterior portion. W e find such modifications of form in other allied genera, and they cannot form the base for establishing distinct generic divisions. The length of the head is nearly one-fourth of the total (without caudal) ; crown entirely bony to the dorsal fin; body much elongate, its greatest depth being only one-half of the length of the head. Mouth toothless. Barbels united by a broad thin membrane ; the maxillary barbel is the longest, extending nearly to the root of the pectoral fin, and provided with several larger and smaller similar appendages. The outer mandibulary barbel is split nearly to the base, so that the mandible appears to be provided with six barbels. Eye of moderate size, its horizontal diameter being more than the width of the interorbital space. Lateral shields very high, covering at least two-thirds of the side of the body; their margin is striated and spinous, the median spine being very strong. Humeral process obtuse, scarcely longer than high. Dorsal spine slender, shorter than the head, slightly serrated along both edges. Adipose fin low and short. Pectoral spine flat and very strong, coarsely dentated along both edges. Pectoral fin forked. Coloration uniform. One specimen, 8 inches long, has been sent by Mr. Bartlett from Xeberos. CALLICHTHYS ARMATUS. (Fig. 1, p. 231.) This species belongs to the group with compressed head. D.j/1. A. 1/6. P. 1/8. V. 6. Head rather higher than long; the height of the body is two-fifths of the total length (without caudal). Maxillary barbels extending to below the eye. Twenty-three series of shields in the upper series; there are four or five azygos shields before the adipose tin. Spines of the fins very strong and long; dorsal spine as high |