29. SILURIDJ5 NOTURUS. 07 



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

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



(Sihtriihc- part Giinther, v, 30-65, 69-220: Heteroptercc, Proteroptercc, aud Stcno- 

 trancMce.) 



* Anterior and posterior nostrils remote from each other, the posterior provided wiih 



a barbel ; voiner and palatines toothless ; barbels 8. (Icta- 

 lurincB.) 

 a. Adipose fin keel-like, adnate to the back; supraoccipital bone free behind. 



NOTURUS, 52. 

 aa. Adipose fin with its posterior margin free. 



6. Premaxillaxy band of teeth with a lateral backward extension on each 



side PILODICTIS, 53. 



6Z). Premaxillary band of teeth truncate behind. 

 c. Caudal not forked. 



d. Eyes concealed beneath the skin GRONIAS, 54. 



< dd. Eyes normal AMIUUTJS, 55. 



cc. Caudal forked ICTALURUS, 56. 



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



with a valve ; teeth on the palate. (Ariince.) 



e. Lower jaw with 4 barbels ARIUS, 57. 



ee. Lower jaw with 2 barbels ^ELURICHTHYS, 58. 



52. .NOTURUS Eafmesque. 

 Stone Cats. 



(Not tints Raf. Amor. Month. Mag. and Crit. Eev. iv, Nov. 1818, 41 : type Nolurus 

 fiai-ns Eafiuesque.) 



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

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

 entirely concealing the bones. Supraoccipital entirely free from the 

 head of the second interspiual. Eyes small. Month anterior, rather 

 large, the 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 upper jaw is either abruptly truncated 

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

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

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

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

 7 branched rays. Adipose fin long aud low, more or less connected 

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

 nate to the body ; the membrane sometimes high and continuous, some- 

 times notched. Caudal fin very obliquely truncated or rounded, in- 

 serted on an equally obliquely rounded base. Bays rapidly decreasing 

 in length iuferiorly ; numerous rudimentary ones present, both above 

 Bull. Nat, Mus. No. 10 7 



