412 CALIFORNIA ACADEMY OF SCIENCES. 



The ventral surface in the adult is almost entirely 

 covered with granules, except a large naked area at base 

 of ventrals; the anus is surrounded with granules. In 

 the young, the belly is almost wholly naked, there being 

 only a few granules in front of the anus, on the sides of 

 the belly and on the throat. 



The spots on the head frequently coalesce into ver- 

 miculations; all the fins are profusely spotted with dark, 

 the spots on the dorsal, pectoral and ventral fins some- 

 times coalescing into cross bars, those on the caudal 

 forming regular transverse series. Dorsal surface of the 

 body with obscure markings, ventral surface plain. 



Eye 3-4 in the snout, 5|-8 in the head, 2-2f in the 

 interorbital. Lat. 1. 26-27. Head 3-3|. 



365. Plecostomus brevicauda. 



Plecostomun brevicauda Giintlier, v, 235, 1864 (Bahia). 

 Habitat: Bahia. 



This species is known only from the types in the Brit- 

 ish Museum. 



366. Plecostomus robinii. 



HypoHtomns robinii Cuv. & Val. Hist. Nat. Poiss. xv, 501, 1840 

 (Trinidad; La Plata); ?? Gill, Syu. Fish. Trinidad, W. I. 46, 

 1858 (Trinidad). 



Plecostomus robinii Giinther, v, 236, 1864 (Bahia) [not C. & V.]; 

 Steindachner, SB. Ak. Wieu, Ixxiv, 1876, Siisswasserfische Siid- 

 ostlichen Brasiliens, iii, 118 (Kio Una near Bahia); Jordan, 

 Proe. U. S. Nat. Mus. 1886, 560 (name only); Eigeum. & Eigenm. 

 Proc. Cal. Acad. 2d Ser. i, 170, 171, 1888 (Eio Una). 



Plecostomus una Steindachner, SB. Ak. Wien, 1878, Ixxvii, 383. 



Habitat: La Plata to Trinidad. 



Head depressed; snout broad, rounded; interorbital 

 slightly convex; no keels on the head. Occipital termin- 

 ating in a short triangular process, bordered by a single 

 large nuchal plate as in punctatus. Scutes not carinate. 

 Humeral keel strong, disappearing between the fourth 

 and sixth plates. Tip of snout naked. 



Eye 4 J in the snout, 7| in the head, 2| in the interor- 

 bital. 



