SOUTH AMERICAN NEMATOGNATHI. 403 



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



Fifty-four specimens. 



Cudajas; Santarem; Mauacapuru; Tonantins; Obidos; 

 Fonteboa; Tabatinga; Hyavary; Sao Paola; Goyaz;TefEe; 

 Para; Iga; Tajapuru. 



Una 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. 



Plecodomus spinosissimus Steindachner, Fisch-fauna des Cauca and 

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

 Guayaquil). 



Habitat: Western slope of Ecuador. 



346. Plecostomus commersonii. 



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

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

 cisco; La Plata). 



Plecostomus commersonii Giiuther, t, 232, 1864 (Rio Grande); Hen- 

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

 dachner, SB. Ak. Wieu, Ixxiv, 1876; Siisswasserf. sildostl. Bras, 

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

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

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

 Santa Cruz; Macacos; Itabapuana). 



Hypostomiis punctatus Cuvier & Valenciennes, xv, 493, 1840 (Rio 

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

 Branco). 



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

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



Plecostomus spinif/er Hensel, Wiegm. Arch. 1870, i, 73 (Rio Cadea). 



Habitat: Southeastern Brazil; Rio 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 



