288 MEMOIRS OF THE CARNEGIE MUSEUM. 



mens collected by Haseman; origin of dorsal some distance behind ventrals, equi- 

 distant from occiput and tip of caudal in the type or from some portion of the snout 

 and ti}) of caudal in the specimens collected by Haseman; fourth or fifth dorsal ray 

 highest, then gradually decreasing in height to the last. Caudal emarginate, the 

 upper lobe pointed, the lower rounded; anal inserted about under the ninth dorsal 

 ray and terminating under about the seventeenth; ventrals inserted nearer tip of 

 snout than to tips of middle caudal rays, reaching to the vent or slightly beyond. 



Sides and back in the San Juan specimens profusely spotted, much less so in 

 the specimens from the Rio Colorado. 



Genus IV. Pygidium 10 Meyen. 



Trichomycterus Valenciennes, in Humboldt, Rec. d'Obs. Zool. et Anat., II, 1833, 



p. 348 (nigricans); not Thrichomycterus Cuvier and Valenciennes, in Humboldt, 



of which it is a misspelling. Gunther, Cat. Fishes Brit. Mus., V, 1864, p. 



272. 



Thrychomycterus Cuvier & Valenciennes, Hist. Nat. Poiss., XVIII, 1846, p. 485 



(misspelled). 

 Thrichomycterus non Cuvier & Valenciennes, Girard, Proc. Acad. Nat. Sci. Phila., 

 VII, 1854, p. 198; Girard, U. S. Nav. Astron. Exped., II, 1855, p. 242 (mis- 

 quoted). 

 Pygidium Meyen, 17 Reise, I, 1835, p. 474 (Juscum). 

 Type. — Pygidium juscum Meyen. 



Skin naked; head depressed, nearly or quite as broad as long, its length 

 five or six times in the length from snout to caudal; body terete, the caudal 

 peduncle compressed, deep; a nasal barbel as long as the head or shorter, on the 

 posterior edge of the anterior nares; two barbels at the angle of the mouth, the 

 upper, connected with the rudimentary maxillary, may reach to the tip of the 



16 7ri>7i5io^, to = a thin rump = the tail much compressed. 



17 In "Archiv fur Naturgeschichte von Dr. Ar. Fr. Aug. Wiegmann, Zweiter Band, Berlin, 1835 

 ( Part. II), p. 269," the original description with addenda appears as follows: 



"Eine neue Gattung der Siluriden, Pygidium, hat Meyen (Reise, I, p. 475), nach einem todten 

 Fische aufgestellt, den er in einem kleinen Bache Peru's antraf. 



"Char. gen. Corpus elongation, caudam versus compressum. Cirri maxillares 4, nasales nulli. 

 Pumas peotorales ut pinnae abdominales duae cum pinna anali circa anum posita;. Pinna adiposa parva. 

 (Die einzige Art P. fuscum ist 5 — 6" lang). Die Gattung bedarf einer genaueren Charakteristik; die 

 gegebene ist dahin zu berichtigen, dass cirri nasales vorhanden sind, und die Ruckenflosse Strahlen hat, 

 ;il 'i keine Fettflosse ist. Die Gattung stent demnaeh nicht Malapterus, sondern Silurus nahe, unter- 

 scheidel sich von diesem (lurch Zahnlosigkeit des Vomer, durch em operculum aculeato-serratum, und 

 durch die writ hinten stehende Riickenflosse. Das Exemplar ist im Berliner Museum." 



