276 MEMOIRS OF THE CARNEGIE MUSEUM. 



< Trichomycteridce Regan, Ann. & Mag. Nat. Hist. (8), VIII, 1911, p. 57. 

 = Trichomycteridce Ribeiro, Archives do Mllscu Nacional, XVI, 1912, p. 219. 



Limits of the family Pygidiid^e. (Plates XL and XLI.) 



Giinthcr, in his "Catalogue of the Fishes of the British Museum," V, 1864, pp. 

 271-277, arranges the then known members of the Pygidiidce under three " Groups," 

 belonging to two of his eight Subfamilies of the Siluridw. His seventh Subfamily, 

 the Siluridce Opisthopterw, consists of his Fifteenth Group, the Nematogenyina 

 (Hcpiapterus and Nematogenys) and the Sixteenth Group, the TricJwynycterina 

 {Trichnmyctcrus (= Pygidium) , Erc?tiophilus , Pariodon). His Eighth Subfamily, the 

 Siluridce Branchicola', consists of his Seventeenth Group, the Stcgophilina {Stego- 

 philus and Vandellia). 



The genus Heptapterus" included in his Fifteenth Group, was shown Ijyus in 

 the American Naturalist, July, 1888, p. 648, to "have no real affinity with the 

 PygidiidcE.^' 



We do not now feel justified in joining the Cetopsince to the family. 



The PygidiidoB, as here understood, are the Pygidiince (exclusive of Pariolius 

 and the Stegophilince of the family, as described by Eigenmann & Eigenmann, in 

 the American Ncduralist, Jul.y, 1888, and Occasional Papers of the California 

 Academy of Sciences, I, 1890. The species known at the time, thirty-six in number, 

 belonging to eight genera, were reviewed in the last named paper. The Cetopsince, 

 included in the papers mentioned, constitute a distinct family. Regan (Ann. & 

 Mag. Nat. Hist. (8), VIII, 1911, p. 574) has united the Pygidiince and Stegopkilince 

 in his Trichomycterince of his Trichomycteridce = Pygidiidce. The family includes 

 the South American Nematognaths without an adipose fin, with the dorsal over or 

 behind the ventrals; posterior air-bladder obsolete; the anterior minute, in two 

 lateral parts, enclosed in bony capsules with a comj^lete osseous floor, united to the 

 exoccipital and epiotic bones proximally and to the suprascapula distally; neural 

 spine of the coalesced vertebrae very low, not as high as that of the vertebrae fol- 

 lowing them; parapophysis of the vertebra? following the capsule short; skull de- 

 pressed, entirely closed in front, without an open space between the osseous roof of 

 the mouth and the ethmoid; vomer and palatines weak, without teeth; clavicles 

 wide, scoop-shaped, meeting below. The place of the adipose fin sometimes occupied 

 in part by numerous accessory caudal rays; none of the fin-rays modified into 

 spines; nares remote from each other, the anterior one frequently provided with 

 a barbel; the maxillary ending in a short barbel; the lower lip usually ending in 



" Related to Ileptaplerus is the genus Phrcatobius, for an account of which see the Appendix to this 

 paper. 



