

SOUTH AMERICAN NEMATOGNATHI. 403 



Head 3|-4. Lat. 1. 28-29. 



Fifty-four specimens. 



Cudajas; Santarem; Manacapuru; Tonantins; Obidos; 

 Fonteboa; Tabatinga; Hyavary; Sao Paola; Goyaz;Teffe; 

 Para; Iga; Tajapuru. 



One specimen, No. 7992, .38 m. long, from Gurupa 

 and another specimen, No. 8021, the exact locality of 

 which is not known, differ in having darker, more regu- 

 lar round spots. All the marginal spines of the scutes 

 are greatly exaggerated; the opercle and preopercle with a 

 marginal series of movable but not truly erectile spines. 



345. Plecostomus spinosissimus, 



Plecostomus spinosissimus Steindachner, Fisch-fauna des Cauca aud 

 Fliisse bei Guayaquil, 46, pi. v, fig. 1-la, 1880 (Elvers near 

 Guayaquil). 



Habitat: Western slope of Ecuador. 



346. Plecostomus commersonii. 



Hypostomus commersonii Valenciennes, Voy. d'Orbigny ix, Atlas ii, 

 pi. vii, fig. 2, 1847; Cuv. &. Val. xv, 495, 1840 (Eio San Fran- 

 cisco; La Plata). 



Plecostomus commersonii Giinther, v, 232, 1864 (Kio Grande); Hen- 

 sel, Wiegm. Arch, i, 73, 1870 (Porto Alegre; Guahyba); Stein- 

 dachner, SB. Ak. Wien, Ixxiv, 1876; Siisswasserf. siidostl. Bras. 

 iii, 124 (La Plata; Eio San Francisco; Eio Jacuhy and Codea; 

 Eio Parahyba; Eio Quenda near S. Cruz; Eio Grande); Eigenm. 

 & Eigenm. Proc. Cal. Acad. 2dSer. i, 168, 1888 (Eio de Janeiro; 

 Santa Cruz; Macacos; Itabapuana). 



Hypostomus punctatus Cuvier & Valenciennes, xv, 493, 1840 (Eio 

 Janeiro); ? Schomburgk, Fish. Guiana, part i, 144, 1841 (Eio 

 Branco). 



Hypostomus subcarinatus Castlenau, Anim. Amer. Sud, 42, pi. xxi, 

 fig. i, 1855 (Eivers of the province of Mines). 



Plecostomus spiniyer Hensel, Wiegm. Arch. 1870, i, 73 (Eio Cadea). 



Habitat: Southeastern Brazil; Eio Plata and its tributaries. 



Head pointed; an indistinct keel from the anterior 

 nares to the occiput, a more prominent keel on the occi- 

 pital bone; the occipital terminating in a triangular pro- 

 cess and bordered behind by a single large plate; nuchal 

 plates bicarinate. Upper lateral scutes more or less 



