29. SILURID^ — NOTURUS. 
07 
posterior margins always free, even if they are imitecl with each other. 
Whenever a nasal barbel is present it belongs to the posterior nostril.” 
{Sihiridcc part Giintlier, v, 30-65, 69-220: Ileterojilerw, rrotcroptcrcc^ aud Steno- 
bninchicc.) 
* Anterior aud posterior nostrils remote from each other, the iiosterior provided with 
a barbel ; vomer aud palatines toothless ; barbels 8. (Icta- 
lurince.) 
a. Adipose fin keel-like, adnate to the back; snpraoccipital bone free behind. 
Notukus, 52. 
aa. Adipose fin with its posterior margin free. 
b. Premaxillary band of teeth with a lateral backward extension on each 
side PiLODiCTis, 53. 
bb. Premaxillary baud of teeth truncate behind, 
c. Caudal not forked. 
d. Eyes concealed beneath the skin Gronias, 54. 
dd. Eyes normal Amiurus, 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. {Ai'iina’.) 
e. Lower jaw with 4 barbels Arius, 57. 
ee. Lower jaw with 2 barbels .diLURiCHTHYS, 58. 
52. — J^OTUKUS Eafinesqne. 
Stone Cats. 
{Xotiirus Raf. Amer. Mouth. Mag. aud Crit. Rev. iv, Nov. 1818, 41: type Noturus 
flaviis Rafiuesqne.) 
Body more or less elongate, anteriorly' subcylindrical, thence more or 
less compressed. Head above ovate and depressed. Skin very thick, 
entii’cly concealing the bones. Snpraoccipital entirely free from the 
head of the second interspinal. Eyes small. Month anterior, rather 
large, the upper jaw nsnally more or less projecting beyond the lower. 
Teeth snbnlate, closely aggregated in a broad band in each jaw, w'hich 
in the lower one is interrnpted by a linear interval and in the upper one 
is continnons. The band in the njtper jaw is either abruptly truncated 
at each end (snbgenns ScMlbeodes) or prolonged backward by a contin- 
nation from the postero-external angle (snbgenns Koturus). Braiichios- 
tegals 9. Dorsal fin situated over the po.sterior half of the interval 
between the pectoral and ventral fins, with a short, sharp siiiiie and 
7 branched ray's. Adipose fin long and low, more or less connected 
with the accessory rays of the caudal fin, not free i)osteriorly, but ad- 
uate to the body' ; tfie membrane sometimes high and continuous, some- 
times notched. Caudal fiu very oblicpiely' truncated or rounded, in- 
serted on an equally' obliquely' rounded base. Ihiy's rapidly decreasing 
in length interiorly ; numerous rudinieutary ones ifreseiit, botli above 
Bull. Nat. Mus. No. 10 7 
