59. aritjs. 145 



five times and four-fifths in the total length (without caudal), the 

 length of the head four times and a third or four times and a sixth ; 

 the greatest width of the head is four-fifths or five-sixths of its 

 length. Occipital process with a median keel, not much longer than 

 broad, extending on to the small basal bone of the dorsal spine. 

 The teeth on the palate form six contiguous patches*. The maxil- 

 lary barbels reach to the base of the ventrals, the outer ones of the 

 mandible to that of the pectorals. Dorsal spine strong, four-fifths 

 of the length of the head, slightly serrated along both edges. Adi- 

 pose fin rather longer than dorsal ; the length of the latter is less 

 than one-half of its distance from the adipose fin. Pectoral spine 

 broader, but not longer, than that of the dorsal fin. Ventral fins 

 much shoHer than pectorals. (Bl.) 

 Surinam. 



10. Arius mesops. 



Bagras mesops, Ciw. ty Vol. xiv. p. 456. 

 D, 1/7. A. 18. 

 The eye is in the middle between the end of the snout and the 

 praeopercular limb. Occipital process twice as broad as long, termi- 

 nating in a small point which is received in a notch of the nuchal 

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

 Ventrals as long as pectorals. (Vol.) 

 Porto Rico. 



11. Arius guatemalensis. 



D. 1/7. A. 19. P. 1/11. 



The height of the body is one-sixth of the total length (without 

 caudal), the length of the head two-sevenths ; head much broader 

 than high, its greatest width being two-thirds of its length. Eyes 

 of moderate size, situated nearer to the end of the snout than to that 

 of the operculum ; the length of the snout is three-fifths of the width 

 of the interorbital space. Teeth on the vomer 

 separated in the middle, forming a pair of small 

 quadrangular patches which are confluent with 

 those on the palatine bones; the latter have a // \^\ 



subelliptic form. All the teeth villiform. The f I \ \ 



maxillary barbels extend nearly to the end of — ' ^ — ' 



the head, the outer ones of the mandible being half as long as the 

 head. Crown of the head granular, the granulations being arranged 

 in radiating streaks. Occipital process some- 

 what broader than long, triangular, with its 

 hinder end truncated ; the basal bone of the 

 dorsal spine small, crescent-shaped. Dorsal 

 spine of moderate strength, not quite half 

 as long as the head, slightly serrated in front 

 and behind ; the first soft ray is longer than 

 the spine, as high as the body. Adipose fin 

 shorter than the dorsal. Caudal deeply forked, with the upper lobe 



* They are, apparently, similar to those of A. herzberqii 

 VOL. V. ' L 



