.--The Brown Cachalote, Pseudosdsura lopbores (Rcichenbach), is a well-known furnariid of northern Argentina and western Uruguay. It is about 10 inches long, crested, and generally rufous in color, and is notable for its domed stick nest "the size of a barrel," "made with enough material to fill a barrow" (Hudson, Birds of La Plata, 1: 232, 1920). In Reichenbach's original description of Homorus lophotes (Handb. spec. Orn., cont. x, Scansoriae A. Sittinae: 172, 1853), the origin of his type specimen was given as "Bolivia" with a query. I have been unable to determine why Reichen- bach questioned the source of this type (which was destroyed in World War II). Hellmayr (Cat. Bds. Americas, 4: 183, 1925) considered "Bolivia" as "no doubt incorrect," and Peters (Check-list Bds. World, 7: 122, 1951) called it "probably erroneous." These later authors may well have considered "Bolivia" an erroneous locality not only because of Reichenbach's query, but because the species was not otherwise known from the country of Bolivia. It is not listed in any of the major papers on Bolivian birds. Carnegie Museum possesses four specimens of Pseudoselsura lophotes collected by Jos Steinbach on 23 and 25 August 1909 and 25 September 1915, at Guanacos, Province of Cordillera, Dept. Santa Cruz, Bolivia (approximately 32 km. east- southeast of Cabezas), altitude 700 meters. These appear to be the only known Bolivian specimens of the species, but they serve to prove that the Brown Cachalote does, indeed, occur in Bolivia. The four specimens have been compared with 39 from Argentina, representing the combined Carnegie Museum and American Museum of Natural History series, and prove to be subspecifically separable. It is conceivable that Pseudoseisura lopbores may ultimately be found to occur else- where in Bolivia, and it thus seems desirable to establish a restricted type locality for nominate lopbores. I therefore so desiguate Guanacos, the one Bolivian locality from which the species is now known. Although the Argentine race is technically the "new" one and must be named, it is, of course, the well-known one and well represented in museums. I shall therefore reverse the usual descriptive comparisons and describe the characters by which the Bolivian (nominate) race is distinguishable from the Argentine. To generalize, the Bolivian specimens are everywhere paler, with lighter brown and rufous colors. Specifically, in the Bolivian birds: 1. The long, anterior crest feathers are more gray-brown, less blackish, with the longest feathers relatively broader. In all specimens of this species, the anterior crest feathers are dark, the posterior rufous; in Bolivian birds there are more long rufous (i.e., fewer dark anterior) feathers in the crest. 2. The upperparts in general (nape, sides of face and neck, back, rump, upper tail coverts) are paler rufous. 3. The tertials are paler, more rulescent (less blackish) brown. 4. The rectrices are paler, the central pair having shafts hardly darker than the webs (in Argentine birds the shafts of the central rectrices are blackish brown). 5. The general tone of the underparts is paler, but this is more subtle than the difference in dorsal coloration; best marked on throat and under tail coverts. 6. The throat and under tail coverts are not only paler rufous, but have the light tips of fresh feathers less whitish, contrasting less with the ground color. The darker bird, which occupies the range as given by Peters (loc. clt.) for the species as a whole, may be called: Pseudoselsura lopbores argentina, new subspecies. Type: Carnegie Museum No. 137487; adult male in freshly molted plumage, collected at La Cocha, Tucumfin, Argentina, 9 August 1956, by Claes Chr. Olrog. The type specimen is one of a small collection of Argentine birds obtained by Carnegie Museum through the generosity of Dr. F. W. Preston. Specimens in the American Museum of Natural History were examined through the courtesy of Dr. Dean Amadon.--KN'r C. PAxs, Carnegie Museum, Pittsburgh, Penn- sylvania.