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 tip 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 imder 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 8an Juan specimens profusely spotted, much less so in 

 the specimens from the Rio Colorado. 



Genus IV. Pygidium'*"' Me yen. 



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. 



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



(missi^elled). 

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

 VII, 1854, p. 198; Girard, U. 8. Nav. Astron. Exped., II, 1855, p. 242 (mis- 

 quoted). 

 Pygidium Meyen,*' 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, deej^; 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 



'° Trvyl&wv. TO = a thill rump = the tail mucli compressed. 



"In "Archiv fiir Naturgeschichte von Dr. Ar. Fr. Aug. Wiegniaun, 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 oincm todten 

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



"Char. gen. Corpus elongatum, caudam versus compressum. Cirri iiuixillares 4, nasales nulli. 

 Pinnic pectorales ut pinnaj abdominalcs duw cum j)inna anali circa anum posita;. Pinna adiposa parva. 

 (Die einzige Art P. Juscum ist 5^6" lang). Die Gattung bcdarf einer gonaucren Charakteristik; die 

 gegebene ist dahin zu berichtigen, dass cirri nasales vorhanden siud, und die Riickenflosse Strahlen hat, 

 also keine Fettflosse ist. Die Gattung steht demnach uicht Malapterus, sondern Silurus nahe, unter- 

 scheidet sich von diesem durch Zahnlosigkeit des Vomer, dureh ein operculum acvleato-serratum, und 

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



