59. ARITJS. 149 



of the head (its own length included), and twice and a half as broad 

 as long. The basal bone of the dorsal spine is quadrangular, slightly 

 narrowed in the middle. ( Vol.) 

 Surinam ; Porto Kico. 



17. Alius passany. 



Bagrus passany, Cuv. 8f Vol. xiv. p. 458. 



D. 1/7. A. 17. 



Similar to A. proops. 



The eye is close to the end of the snout and remote from the pras- 

 opercular limb ; the lower jaw is the longer. Teeth on the palate 

 and barbels similar to those in A. proops ; occipital process shorter 

 than in that species ; basal bone of the dorsal spine subcrescentic. 

 Ventrals longer than pectorals. ( Vol.) 



Cayenne. 



18. Arius caerulescens. 

 D. 1/7. A. 17. P. 1/10. 



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

 length (without caudal), the length of the head thrice and a half or 

 thrice and two-thirds ; head much broader than high, its greatest 

 width being three-fourths of its length. Eyes rather small, their 

 diameter being one-half of the extent of the snout, two-sevenths of 

 their distance from the gill-opening, and one-third of the width of 

 the interorbital space. The teeth on the palate 

 form a slightly curved band, composed of two 

 vomerine patches which are much broader than 

 long, and of a pair of palatine patches which 

 are subcontinuous with, scarcely broader and 

 longer than, those of the vomer. The bar- 

 bels of the maxillaries extend to the middle, the outer ones of the 

 mandible to the base of the pectoral. Crown of the head granular ; 

 occipital process broader than long, subtri- 

 angular, subtruncated behind, and slightly 

 raised along the median line ; the basal bone 

 of the dorsal spine is subtriangular, small. 

 Dorsal spine of moderate strength, more than 

 half as long as the head, granulated in front 

 and slightly serrated behind ; the first soft ray 

 is as high as the body. Adipose fin shorter 

 than the dorsal. Caudal deeply forked, with 

 the upper lobe longest, its length being nearly 



equal to that of the head. Pectoral spine serrated along its inner 

 edge and on the extremity of its outer edge ; it is as long as the 

 head without snout. Ventral fin shorter than pectoral. Sides steel- 

 blue, iridescent, blackish towards the back, and silvery below. Ver- 

 tical fins black ; inner side of the paired fins blackish. 



Guatemala. 

 a-b. Fine specimens, 12 inches long. Huamuchal. From the Col- 

 lection of Messrs. Godman and Salvin. 



