74 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY II. 



Genus ICHTH^LURUS,* {Rafinesgue) Gill. 



Ictnlurus, Rafinesque (1820), Ichtbyologia Obiensis, 61. 

 ElUops, Rafinesque (1820), Ichtbyologia Obiensis, 62. 

 Syncchoglams, Gill (1850), Annals Lye. Nat. Hist, vii, 39. 

 Ictalurus, Gill (1862), Proc. Boston Soc. Nat. Hist. 41. 

 Ichthcelui-us, Cope (188y\ Jouru. Acad. Nat. Sci. Pbila. 237. 



Etymology. — ixO^Qt fi^li 5 aiTiOvpog, cat. 

 Type. — Silurm xnmctatuti, Rafinesque. 



Body elongated, slender, and much compressed. The caudal peduncle 

 is short but slender, and presents behind the anal an elongated ellipti- 

 cal section. 



Head conical in profile, compressed, and with the sides sloping down- 

 ward and outward. The supraoccipital bone is prolonged backward, and 

 its emarginated apex receives the acuminate anterior point of the second 

 interspinal. The skull is covered by a thin tense skin, through which 

 the sculpture of the bones is apparent. Eyes large and almost entirely lat- 

 eral. Mouth small, transverse, and terminal. The upper jaw protrudes 

 beyond the lower. Teeth subulate and aggregated into a short, laterally 

 truncated band on each jaw. Branchiostegal rays, 8 or 9. Dorsal tin situ- 

 ated over the interval between the pectoral and ventral fins, higher than 

 long, with one long spine and usually six articulated rays. A<li- 

 l)ose fin pedunculated over the posterior portion of the anal. Anal tin 

 long, and provided with from 25 to 35 rays; it commences near the 

 anus. Ventral fins each with one simple and seven branched rays. 

 Pectoral fins each with a stout spine, retrorse-serrate within, and about 

 nine branched rays. The serrae of the pectoral spine vary with age 

 and circumstances, and do not in this genus give good specific charac- 

 ters. Caudal fin elongated and deeply forked, with the lobes equal and 

 pointed. 



The genus Ichthcehirus is at once recognized by the forked caudal fin, 

 its silvery or olivaceous colors, and by its compressed, elongated, and 

 slender body, which give to it a peculiarly graceful appearance, very 

 unlike that of the stout, obese, and large-headed AniiuH. The head is 

 smaller in proportion than in Amiuriis, more compressed, and not cov- 

 ered by so thick a skin ; the mouth is proportionally much smaller. 

 But the only invariable generic distinction resides in the mode of inser- 



* The characters of the genera of SiluridoB as here given are arranged from Prof. 

 Gill's Report on Ichthyology of Captain Simpson's Explorations Across the Great Basiu 

 of Utah, pp. 416-431, with some additions and modifications. 



