234 MR. G. A. BOULENGER ON [Apt. 7, 



7. Arius commersonii, Lacep. 



Notes on the habits and development of this Siluroid in the Laguna 

 dos Patos have been published by Dr. v. Ihering, Biol. Centralbi. viii. 

 1888, p. 268. 



8. Genidens cuviert. Cast. 



9. Callichthys asper, Q. & G. 



I agree with the Eigenmanns in referring G. affinis, Gthr., and 

 G. hemiphractuSy Hens., to this species. The Rio Grande specimens 

 have usually ^ scutes ; and I may add that we have a specimen from 

 Bahia with as many as |y. 



10. Callichthys (Corydoras) paleatus, Jen. 



11. LORICARIA ANUS, Val. 



In a large specimen, 420 millim. long, the length of the first 

 dorsal ray is l^-^ in the length of the head (to extremity of occiput), 

 and the diameter of the orbit (without the notch) is 4| in the length 

 of the snout. In a small specimen, measuring 170 millim., the 

 length of the first dorsal ray is 1^ in the length of the head, 

 and the diameter of the eye 2| in the length of the snout. Two or 

 three minute teeth are present on each side of the upper jaw. Upper 

 caudal lobe considerably longer than the lower. 



12. LoRiCARiA LIMA, Kner. 



Although I have examined but three specimens, two of which I 

 would refer to L. strigilata, I am much inclined to agree with 

 Dr. V. Ihering {in litt.) in regarding L. strigilata and L. cadeoB of 

 Hensel as based on variations of L. lima. 



13. Otocinclus nigricauda, sp. n. (Plate XXV. fig. 3.) 

 D. 1/7. P. 1/5. V. 1/5. A. 1/5. L. lat. 23-25. 



Closely allied to O. affinis, Stdr., but snout more rounded, eye 

 rather smaller, its diameter two fifths the length of the snout, and 

 ventral shields more numerous and irregular, forming five to seven 

 longitudinal series. The coloration is very different from that of 

 O. affinis. Dark olive-brown above ; dorsal, anal, and paired fins with 

 the rays barred black and white ; caudal deep black, with the outer 

 rays spotted with white. 



Total length 42 millim. 



Several specimens. 



14. Plecostomus commersonii, Val. 



15. Ch^tostomus cirrhosus, Val. (Plate XXVI. fig. 1.) 



I give figures illustrating the very marked differences between the 

 heads of male and female as shown by specimens from Dr. v. Ihering's 

 collection. In addition to the rostral appendages and the stronger 

 praeopercular armature, the male differs in tlie longer pectoral fin, 

 which extends to the middle of the ventral spine instead of to its 

 base. 



