230 DR. A. gOnther o> new AMERICAN FISHES. [Mar. 20, 



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 tlie 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 AmpuUarias 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. We find such modi- 

 fications of form in other alHed 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 elon- 

 gate, its greatest dejith being only one-half of the length of the 

 head. Mouth tootliless. Barbels united by a broad thin mem- 

 brane ; 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. Colora- 

 tion 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. 1/1. A. 1/6. P. 1/8. V. 6. 



Head rather higher than long ; the height of the body is two- 

 fifths of tlie total length (without caudal). Maxillary barbels ex- 

 tending 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 



