172 SILUIUDJS. 



61. Arius melanopus. 

 D. 1/7. A. 21. P. 1/10. 



This species is closely allied to A. laticeps, but has the fin-spines 

 shorter. 



The height of the body is contained five times in the total length 

 (without caudal), the length of the head four times and a third ; 

 head somewhat broader than high, its greatest width being three- 

 fourths of its length ; the occiput and nape are finely granulated ; 

 occipital process subtriangular, as long as broad, with the lateral 

 margins somewhat concave, and with the median ridge a little ele- 

 vated. The longitudinal groove in the middle of the crown of the 

 head is indistinct, narrow, linear behind, scarcely extending to the 

 base of the occipital process. The teeth on the palate are obtusely 

 conical, and form two rather small subovate patches, apart from 

 each other, and situated on the front part of the palate. The maxil- 

 lary barbels do not quite extend to the middle of the pectoral fin. 

 Dorsal spine of moderate strength, scarcely serrated anteriorly, equal 

 in length to the distance of the gill-opening from the anterior margin 

 of the orbit, or even somewhat shorter. Adipose fin small, the 

 length of its base being less than that of the dorsal. Pectoral spine 

 nearly as long and strong as that of the dorsal fin, very strongly ser- 

 rated interiorly. Porus axillaris nearly as wide as a nasal opening. 

 The upper (inner) surface of the ventral fins deep black, the lower 

 (outer) white. The inner surface of the pectorals blackish. 



Rio Motagua. 



d-b. From 8 to 9 inches long. From Mr. Salvin's Collection. 



62. Arius arenatus. 

 Arius arenatus, Cuv. fy Val. xv. p. 106. 



B. 6. D. 1/6. A. 20. P. 1/9. 

 The distance betvveen the end of the snout and that of the occipital 

 process is contained thrice and a third in the total length (with the 

 caudal); basal bone of the dorsal spine small. The teeth on the 

 palate form two large ovate patches which touch each other ante- 

 riorly. The maxillary barbel extends to the middle of the pectoral 

 fin. Adipose fin small. {Val.) 

 Cayenne. 



The typical specimen, 7 inches long, is in the Leyden Museum. 



63. Arius fissus. 



? Pimelodus afbidus, Spix, Pise. Bras. tab. 7. fig. 1. 

 PPimelodus spixii, Agass. in Spix, Pise. Bra$. p. 19. 

 ? Arius spixii, Cuv. 8f Val. xv. p. 76. 

 Ajius fissus, Cuv. 8f Val. xv. p. 107. 



D. 1/7. A. 20-21. 

 The lengtn of the head is one-third of the total (without caudal). 

 The distance between the end of the snout and that of the occipital 



