422 EXPLORATIONS ACKOSS THE GREAT BASIN OF UTAH. 



The anus is situated some distance in advance of the anal iin. 



Tlie Noturi are at once recognized by the peculiarly-formed caudal fin and its 

 oblique insertion on the peduncle, and by the ovate head, with the transversely-depressed 

 nape and median longitudinal groove. 



For our earliest information of a species of this genus, wc are indebted to Dr. 

 Samuel L. Mitcliill; but the description of that naturalist is incorrect, or, at least, his 

 interpretation of the characters observed is erroneous. Subsequent naturalists have, 

 therefore, been much deceived as to its affinities. 



The principal error in Mitchill's description is the assertion of the aljsence of an 

 adipose fin. But this statement is readily reconciled with the features of Nofurns 

 when it is remembered how low that fin is, and how it unites with tlie caudal. 

 Mitchill drew attention to the peculiarity of the caudal, and described it as com- 

 mencing an inch behind the dorsal fin, and thence "continued quite round the tail, and 

 almost to the anal tin. The form is lanceolated and pointed," and "it may be compared 

 to the tail of an eel; the resemblance is nearer to that of a tadpole, when it approaches 

 the period of conversion to a frog." The peculiarities thus noticed and the rest of 

 Mitchill's description leave no doubt as to the true affinities of the Sihirus gijyhms, and 

 as to the correctness of Rafinesque in afterward referring it to his genus Notiinis. 



Mitchill observed tliat "the want of serrae to the spines, and of a second dorsal 

 might lead some to remove this fish from the Siliiri. family ; but to avoid needless 

 innovation, I retain him here." ]\Iitchill, when inditing that remark, nuist have for- 

 gotten that the type of SHioks was Avithout an adipose fin, and that the presence of 

 such a fin was consequently an exceptional rather than a normal character of the 

 Linnaean genus, althoiigh the greater portion of its species were provided with it. The 

 want of seiTa? to the spines is not of as much value as Mitchill supposed. 



Dr. De Kay, in his Fauna of New York, introduced Mitchill's description of 

 Sihints (/i/riiius at the end of the suite of the Pimdodi of the State described in his 

 work, and remarked that "on account of its dorsal spine it cannot be admitted into 

 that genus " (Silurus Val.) ; and the same spine being smooth, and not serrated, ex- 

 cludes it from Schilbe. Its natural position in a general arrangement of the Siluridce 

 would seem to be between Schilbe and Cc(o2)sis, forming a passage, by its simply 

 spinous anterior dorsal and pectoral ray, from one to the other. It may be thus 

 characterized: "No adipose fin; simple spines to the dorsal and pectoral; anal long; 

 caudal pointed, not united to the anal." Important details respecting the teeth are 

 Avanting to complete the character. 



Having already noticed the ti'ue relationship of Sihirus gi/rii/us, it necessarily 

 folloAvs that there is no near affinity between it and the genera noticed by De Kay. 



The description of Mitchill and the remarks of Dr. De Kay have also led Dr. 

 Bleeker into error. That learned ichthyologist, in his Monograph of the Siluri, has 

 formed a distinct genus for the Silurus f/i/riiius, Avliich he has named Schilbeodes, and 

 Avhich is interposed lietween llcnmtogciujs of Girard and Trichomi/cterus of Cuvier and 

 Valenciennes, in the subfamily of Silurichthyoidci and the group of Trichomycterini. 

 Bleeker's generic characters are the following: 



