FBOM THE RIO JURUA. 425 



17. Ch^tostomus BAcm, sp. n. (Plate XLI. fig. 1.) ~ 



About 16 teeth on each side in each jaw. Depth of body 4^ times in total length, 

 length of head 3 times. Head very slightly longer than broad, entirely rough with 

 small spines ; snout rounded ; diameter of eye 6 times in length of head, 3 times in 

 length of snout, 3| times in interorbital width ; no postorbital groove; longest erectile 

 prseopercular spines as long as diameter of eye ; barbel minute, hardly ^ diameter of 

 eye. Thi'oat and belly covered with small rough shields. Dorsal I 7 ; first ray a 

 little shorter than head. Pectoral spine as long as head, covered with small spines, 

 reaching middle of ventral. Ventral I 5, | length of head. Anal I 4. Candal 

 obliquely truncated, lower ray 1| as long as upper. Shields on body rough with small 

 spinules, without keels, 26 in a longitudinal series. Pale olive, with rather indistinct, 

 large, rounded, darker spots ; caudal with dark cross-bars. 



Total length 110 millim. 



A single specimen. 



Nearest allied to Ch. ologospilus Gthr., which dififers in the forked caudal fin and 

 the naked belly. 



18. HyPOPTOPOMA GUENTHERI Blgr. 



19. LORICARIA ROSTRATA Spix. 



20. LORICARIA FIL.iMENTOSA Stdr. 



21. LoRiCARiA ACIPENSERINA Kner. 



22. AcESTRA 6LADIUS, sp. n. (Plate XLI. fig. 2.) 



Length of head 3^ times in total length. Snout exceedingly long and narrow, 

 sword-shaped, the prse-oral part as long as the rest of the head, the length of the 

 rostrum 14 times its least width ; no bristles on the head ; eye small, its diameter 3^ 

 times in interorbital width ; upper angle of gill-opening nearer origin of dorsal than 

 tip of snout. Dorsal I 6 ; first ray ^ length of head. Pectoral not reaching ventral. 

 Anal 1 5 ; first ray f length of head. Caudal deeply emarginate, with the outer rays 

 produced into very long filaments. Body moderately depressed; 7 scutes between 

 occiput and dorsal, the second and third more than twice as broad as long ; 3 series of 

 ventral scutes, 6 on each side between pectoral and ventral. Tail strongly depressed. 

 32 scutes along each side, those on the body forming two obscure keels coalescing a 

 little behind the vertical of the anal. Uniform olive-grey ; fins white, pectorals and 

 ventrals with grey bars, caudal with a black band along the upper lobe. 



Total length 215 millim. 



Two specimens. 



Closely allied to A. oxyrhynclia Kner. Distinguished by tlie absence of bristles on 

 the snout and the broader dorsal scutes. 



