208 SILURIU^. 



linely serrated ; the first is very large, reaching downwards to the 

 humeral process and to the thoracic plates, which are naked, and 

 bent upwards on the sides of the body. A single broad shield before 

 the root of the caudal, on the upper and lower surfaces of the tail. 

 The humeral process is elongate, not tapering behind, terminating 

 in a rounded extremity before the first lateral shield. Eye rather 

 large, its diameter being two-thirds of the length of the snout. The 

 maxillary barbels are provided with long tentacles, and extend to 

 behind the base of the pectoral fin ; the four mandibulary barbels 

 are short, and united at their base by a membrane. The upper and 

 lower jaws with a narrow band of minute teeth. Brown, with blackish 

 spots. (Kner.) 

 Rio Guapore, 



6. Oxydoras stenopeltis. 



Oxydoras stenopeltis {Heck.}, Kner, Sitzqsber. Wien. Acad. 1855, xvii. 

 p. 142. fig. 7. 



D. 1/6. A. 13-14. L. lat. 35-36. 



Adipose fin short. Lateral shields high, at least half as high as 

 the body, each with several series of small spines ; five or six shields 

 between the dorsal and adipose fins. Humeral process striated, 

 obliquely truncated behind, not much broader than, and extending 

 to the posterior third of, the pectoral spine. Eye rather large, its 

 diameter being equal to its distance from the anterior nostril. The 

 bases of the barbels are united by a membrane : those of the maxil- 

 larj' are provided with a series of small tentacles, and extend to 

 behind the root of the pectoral ; those of the mandible are short and 

 covered with papillae. Teeth none, or quite rudimentary. Brownish 

 above, whitish below. {Kner.) 



Rio Negro. 



7. Oxydoras lipophthalmus. 



Oxydoras lipophthalmus, Kner, Siizgsber. Wien. Acad. 1865, xvii. p. 147. 

 fig. 8. 



D. 1/6. A. 12. P. 1/9. V. 7. L. lat. 37-38. 



Adipose fin short. Lateral shields small, half covered with thiii 

 skin, smooth, with the posterior margin serrated. Tail without 

 shields on its upper and lower surfaces. Humeral process wrinkled, 

 obliquely rounded behind, much broader than, and extending back- 

 wards to the middle of, the pectoral spine. Eye large, covered with 

 an adipose membrane which is produced closely to the hind nostril. 

 The bases of the barbels are united by a broad membrane fringing 

 the lower jaw; all are provided with small tentacles, and the max- 

 illary and outer mandibulary barbels are bifid ; the former extend 

 scarcely to the gill-opening, and the latter are rather more than half 

 as long. Teeth none, or quite rudimentary in the lower jaw. 

 Brownish above, whitish below. 



Rio Negro ; River Capin. 



a. Fine specimen. River Capin. Purchased of Mr. Stevens. 



