50. ARIDS. 



155 



total length (without caudal), the length of the head four times or 

 four times and a third. Head depressed, broader than high, its 

 greatest width being three-quarters of its length ; snout of moderate 

 length, obtuse, its extent being three-fifths of the width of the in- 

 terorbital space. The eye is situtited much nearer to the end of the 

 snout than to that of the operculum ; its diameter is one-sixth of 

 the length of the head, and two-sevenths of the width of the inter- 

 orbital space. The teeth on the palate are villi- 

 form, and form a pair of separate, irregularly 

 rounded patches. The maxillary barbels extend 

 to the base or beyond the middle of the pectoral 

 fin, the outer ones of the mandible to its root or 

 to its middle. The crown of the head is slightly 

 granulated ; the occipital process is triangular, as long as broad, 

 provided with a sharp median ridge ; basal bone 

 of the dorsal spine small, crescent-shaped. Dor- 

 sal spine long and rather strong, nearly as long- 

 as, or shorter than, the head, slightly serrated 

 in front and behind ; the length of the first soft 

 ray exceeds that of the spine and of the head. 

 Adipose .fin much shorter than dorsal. Caudal 

 deeply forked, with the upper lobe longest, one- 

 fifth of the total length. Pectoral spine as strong 

 and long as that of the dorsal fin, serrated along 

 both edges. Ventral shorter than pectoral. Fins 

 and barbels black. 

 River Niger. 



ff, b. Eleven and nine inches long. Niger Expedition. 



c. Thirteen inches long. Lagos. From the Collection of J.Wood, Esq. 



^. South American species. 



3(». Alius milberti. 



Arius milberti, Cut: ^ V(d. xv. p. 74 ; Hyrtl, Denkschr. Acad. Wks. 

 Wivn, 1859, xvi. p. 17. 



D. 1/7. A. 18. P. 1/10. Vert. 19/83. 

 The height of the body is contained five times and a half in the 

 total length (^vithout caudal), the length of the head thrice and two- 

 thirds ; head depressed, much broader than high, its greatest width 

 being eijual to its length without snout. Eyes situated much nearer 

 to the end of the snout than to that of the opcrcle. Teeth on the 

 vomer in two small, separate groups, M'hich are either 

 separate from, or continuous with, the much larger 

 rounded patches of palatine teetli. All the teeth 

 \illiform. The maxillary barbels extend to, or nearly 

 to, the end of the operculum ; the outer ones of the 

 mandible are half as long as the head. Crown of 

 the head granulated ; occipital process rather broader than Ion" 



tri- 



angular, with a ridge along tlie middle : the basal bone of the dorsal 



