29. SILURID^ — NOTURUS. 97 



posterior margins always free, even if tliey are united with each other. 

 Whenever a nasal barbel is present it belongs to the posterior nostril." 



(SUuridw part Giiutlier, v, 30-G5, G9-220: Heterojitcrce, ProUroptcra; and Stcno- 

 branchicc.) 



*Auterior and posterior nostrils ronioto from each other, the posterior provided with 

 a barbel ; vomer and palatines toothless ; barbels 8. {Icta- 

 hirina'.) 

 a, Adipose fin keel-like, adnute to the baek; snpraoccipital bono free behind. 



NoTUiius, 52. 

 aa. Adipose fm with its postcu'ior margin free. 



b. Premaxiliary band of teeth with a lateral backward extension on each 



side I'lLODicTis, 5:3. 



bb. Premaxiliary band of teeth trnneate behind. 

 c. Candal not foiked. 



d. Eyes concealed beneath the skin GnoNiAS, 54. 



^ dd. Ejes normal Amicrus, 55. 



cc. Caudal forked Ictalurus, 56. 



** Anterior and iiosterior nostrils close together, neither with a barbel, the posterior 

 with a valve ; teeth on the palate. (Ara)ia!.) 



e. Lower jaw with 4 barbels Arius, 57. 



ec. Lower jaw wifh 2 barbels /Elurichthys, 58. 



52.— NOTBJEiUS Rafinesqne. 



/Stone Cats. 



{Xoiurus Raf. Amer. Month. Mag. and Crit. Rev. iv, Nov. 1818, 41: type Nolurus 

 ^a7'»s Ralinesque. ) 



Body more or less elongate, anteriorly subcylindrical, thence more or 

 less compressed. Head above ovate and depressed. Skin very thick, 

 entirely concealing the bones. Snpraoccipital entirely free from the 

 head of the second interspinal. Eyes small. Mouth anterior, rather 

 large, tlie upper jaw usually more or less projecting beyond the lower. 

 Teeth subulate, closely aggregated in a broad band in each jaw", which 

 in the lower one is interrupted by a linear interval and in the upper one 

 is continuous. The band in the upi)er jaw is either abruptly truncated 

 at each end (subgenus IScMlheodes) or prolonged backward by a contin- 

 uation from the postero-external angle (subgenus Noturwi). Branchios- 

 tegals 9. Dorsal fin situated over the posterior half of the interval 

 between the pectoral and ventral fins, Avitli a short, sharp spine and 

 7 branched rays. Adipose lin long and low, more or less connected 

 with the accessory rays of the caudal fin, not free posteriorly, but ad- 

 nate to the body; tlie membrane sometinies high and continuous, soine- 

 tinics notclied. Caudal fm very obliiiuely truncated or romided, in- 

 serted on an equally obliijuely rounded base, liays rapidly decreasing 

 in lengtli inleriorly ; numerous rudimentary onOs present, both above 

 Bull. Nat. Mus. No. IG 7 



