SILURID^. 79 



of the species with those previously known. So far as I can judge 

 from the figure, this species is an affine of T. robustus, liaving, like that 

 species, the eye anterior and the number of anal rays intermediate (28 

 or 29), but differing in the greater slenderness of the body. 



Genus AMIURUS, {Rafinesque) Gill 



Siluriis et Pimelodus sp., Lixn^us, and all writers prior to ISfi-i. 



Aviciurus, Rafinksquk (1820), Ich. Obienais, 65 (as section under subgenns Idalurus of 



Pimelodus). 

 Amiurus. Gill (186->), Proc. Bost. Soc. Nat. Hist. 50, and of recent writers generally. 

 Ameiints, Cope (18G4), Proc. Acad. Nat. Sci. Pbila. 231. 

 Gronias, * Cope (18G4), Proc. Acad. Nat. Sci. Pliila. 2:51 (G.nigrilabria). 



i^TYMOLOGY.— rt, privitive ; ueiovpo^, curtailed, in allnsiou to the entire caudal fin. 



Type. — Silurus cupreus Ratinesque. 



Body moderately elongated, robust, anteriorly vertically ovate, and 

 scarcely compressed ; caudal peduncle also robust, but much compressed, 

 and at its end evenly convex. 



Head large, wide, laterally expanded, above ovate and in profile cunei- 

 form ; supraoccipital extended little posteriorly and terminating in a 

 more or less acute point, which is entirely separate from the second in- 

 terspinal buckler; the skin covering the bones is thick. 



Eyes rather small, in one species covered by the skin ; mouth large, 

 terminal, transverse, the upper jaw in most species the longer; jaws 

 often equal, the lower in one or two species distinctly projecting. 



Teeth subulate, aggregated in broad bands on the iutermaxillaries 

 and dentaries; the intermaxiUary band is convex in front, of equal 

 breadth, and abruptly truncated near the insertion of the iutermaxil- 

 laries; the lower dental band is anteriorly semicircular, atteouated to 

 the angles of the mouth. 



Branchiostegal membrane on each side with eight or nine rays in 

 typical species, ten or eleven in two or three aberrant species; dorsal 

 situated over the interval between the pectorals and ventrals, higher 

 than long, with a pungent spinous ray dentate behind, and about six 

 branched rays; adipose tin short, inserted over the posterior half of the 

 anal ; anal fin of moderate length, with from fifteen to twenty-six rays, 

 the usual number being twenty or twenty-one; caudal fin short, usually 

 truncate when spread open, slightly emarginate when not expanded.— in 

 species related to Ichthcclurus more or less deeply forked, in some other 

 species rounded; when the cauda l fin is forked the lobes are usually un- 



* Prof. Cope thus defines this genus :— *' Head broad, depressed ; supraoccipital bono 

 posteriorly free ; branchiostegal m.-mbrane with ten rays ; anterior dorsal spine stout: 

 posterior (adipose) fin separated from caudal; ventrals with eight rays; eyes rudi- 

 meutal, covered by the corium; natatory bladder present." 



