234 MR. G. A. BOOLENGER ON [Apr. 7, 



7. Arius commersonii, Lacep. 



Notes oil 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 cuvieri. Cast. 



9. Callichthys asper, Q. & G. 



I a?ree with the Eigenmatins in referring C. affinis, Gthr., and 

 C. hemlphractus, Hens., to this species. The Rio Grande specimens 

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

 Bahia with as many as ^. 



10. Callichthys (Corydoras) paleatus, Jen. 



11. LORICARIA ANUS, Val. 



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

 dorsal ray is ly^jj 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 miUim., 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, Kucr. 



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

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

 Dr. V. Ihering {in litt.) in regarding L. strigiluta and L. cadece 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^etostomus cirrhosus, Val. (Plate XXVI. fig. 1.) 



I give figures illustrating the very marked differences between the 

 lieads 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 the longer pectoral fin, 

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

 base. 



