

SOUTH AMERICAN NEMATOGNATHI. 145 



Head 5; depth 8; D. 7; A. 24. 



Two specimens .045-.05 m. Maldonado. Th. Carey. 



XVIII. ACENTRONICHTHYS. 



Acentronichthys E. & E. Proc. Cal. Acad. Sci. 2d Ser. i, 

 28, 1889 (A. leptos). 



Type: Acentronichthys leptos E. & E. 



Caudal widely forked; occipital process small, not con- 

 tinued to the dorsal; fontanel extending to the base of 

 the occipital. Orbit without a free margin. Dorsal and 

 pectorals without spines; ventrals under anterior half of 

 dorsal; anal long. Allied to Heptapterus. 



ANALYSIS OF THE SPECIES OF ACENTRONICHTHYS. 



a. Adipose fin confluent with the caudal fin; first ventral ray below third 



dorsal ray; origin of anal slightly behind origin of adipose. D. 7; A. 



19. Head "i\. leplos 104. 



aa. Adipose fin not confluent with the caudal fin, its distance from the 



caudal equal to the length of its base; first ventral ray in front of the 



vertical from origin of dorsal. 



6. D. 7; A. 18. Depth more than 2 in the head, which is 6 in the 

 length. surinamensis 105. 



66. D. 8; A. 20. Head 5-6; depth 8-9; caudal forked, the upper lobe 

 much the longer; anal fin long and low, its origin midway between 

 end of dorsal and origin of adipose. (Steindachner.) collettii 106. 



104. Acentronichthys leptos, 



E. & E. Proc. Cal. Acad. Sci. 2d Ser. i, 29, 1889 (Sao Matheos). 

 Type: No. 7532; one specimen .105 m. Sao Matheos. Hartt & Cope- 

 land . 



Extremely elongate, the depth of the caudal peduncle 

 not much less than the greatest depth. Head long and 

 narrow, not greatly narrowed forward, its width If in 

 its length. Cheeks steep. 



Eye minute, one orbital diameter nearer tip of snout 

 than to end of opercle; interocular about 2 in the snout. 

 Maxillary barbels reaching beyond middle of pectoral, 

 mental and postmeiital beyond base of pectoral. Mouth 

 wide, terminal, the jaws equal, its width 2 in the length 

 10 



