784 FISHES—SILURIDA. 
Third superior pharyngeal bone wanting, or small and resting on the fourth, second di- . 
rected backwards; one or two pairs of basal branchihyals; suboperculum wanting; pre- 
maxillary forming mouth-border above; interclavicles present.” A large order, in some 
respects intermediate between the Sturgeons and the Cyprinide. The leading family is 
the Siluride. 
*Opercle present ; dorsal fin inserted in front of the ventrals. . . SILURIDA. 7. 
IM AIR SE IEE S SJE WW 185 ICID) ath AN Tel Id, ON Wo IES JEL ys) 
This family includes such of the Nematognathi as have the rayed dorsal fin short, and 
placed in edvance of the ventrals, and the operculum developed. The variation in appear- 
ance among the members of this family is great, some having the skin naked, others hav- 
ing it covered with bony plates of various forms. The American fresh water species, some 
thirty in number, agree in having the body naked; the head with eight long barbels 
whereof the maxillary bones form the base of the longest pair; no subopercle; top of 
head not mailed; dorsal and pectoral fins each with a pungent spine, which is often 
serrate ; adipose fin present, without rays; gill openings wide. 
There are upwards of seven hundred species of Siluridw# known, referred to about one 
hundred genera. They are most numerous in the fresh waters of South America, and 
are numerous enough in North America aud Africa. A few occur in Europe, and some 
are marive. Oar species are valued for food in proportion to their size. They mostly 
inhabit lakes and sluggish streams, and are usually very tenacious of life. ‘ 
* Adipose fin, with its posterior margin free, not adaate to the body, nor connected 
with the caudal fin. 
a. Band of teth on the premaxillaries, without lateral backward processes. 
b  Supraocecipital bone produced backward from the skull, receiving the pointed 
anterior end of the second interspinal (bone at the base of the dorsal fin), thus forming 
a continuous bony bridge from the head to the dorsal; (slender silvery species, with small 
mouth and forked caudal fia) ‘ : j 5 0 : ICHTHZLURUS. 10. 
bb. Supraoccipital bone not produced, falling short of the interspinal, the bony 
bridge being therefore interrupted ; (stcut dusky-colored species, with larger mouth and 
less forked or truncate caudal fin. : 6 : : ; Amiurus 11. 
aa. Band of teeth on the premaxillary, with a strong backward extension on each 
side; lower jaw longest; anal fin short. ; : PELODICHTHYS 12. 
** Adipose fin low, keel-like, adnate to the rate and usually continuous with the 
caudal fin. : : : 6 5 ; . : Norurvus. 13. 
GENUS 10. ICHTHALURUS. Rafinesque. 
Ictalurus, RAFINESQUE (1820), Ichthyologia Ohiensis, 61. 
Elliops, RAFINESQUE (1620), Ichthyologia Ohiensis, 62. 
Synechoglanis, GILL (1859), Annals Lyc. Nat. Hist., vii, 39. 
- Ictalurus, GIL (1862), Proc. Boston Soc. Nat. Hist., 41. 
Tchihelurus, Copr (1669), Journ. Acad. Nat Sci., Phila., 237. (Corrected orthography.) 
Type, Silurus punctatus, Rafinesque. : 
Etymology, Jchthus, fish; ailourus, cat. 
Body elongated, slender, and much compressed. The caudal peduncle is short but 
slender, and presents behind the anal an elongated elliptical section. 
