422 KXPLORATKXNS ACROSS THE GREAT BASIN OF UTAH. 



The Xnturi 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 alld median longitudinal groove. ' 



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



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

 therefore, been much deceived as to its affinities. 



Tlie principal error in MitchuTs description is the assertion of the absence of an 

 adipose Bn. But this statement is readily reconciled with the features of Xohcru, 

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



dmost to the anal fin. The form is lanceolate*! and pointed; 1 ami -it may be compared 

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

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

 ditchhTs description leave no doubt as to the true affinities of the Siturus gyrinus, and 

 .s to the correctness of Kafinesque in afterward referring it to his ^enus Xotimt*. 



Mitchill observed that -the want of seme to the spines, and of a second dorsad 

 night lead some to remove this fish from the Siluri family: but to avoid needless 



rotten that the type of SUurus was without an adipose tin, and that the presence of 

 uch a tin was consequently an exceptional rather than a normal character of the 

 anmvan genus, although the greater portion of its species were provided with it. The 

 vant of soitjv to the spines is not of as much value as Mitchill supposed. 



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

 Mums gyrinus at the end of the .wife of the Vhnvhdi of the State described in his 

 vork, and remarked that -on account of its dorsal spine it cannot be admitted into 



th; 



'deT!t l h- 



oi^^^iiraf^n 



.pine being sin ooth, and not 

 in a general arrangement of 



IhoVL- 



eh; 



uld seer 

 idal poii 



,i to be between Srhi/hr and t 

 terior dorsal and pectoral ray, 



.ted, not united to the anal." ] 



ktopsis, forming a passage, b; 

 from one to the other. It i 



es to the dorsal and pectoral 

 mportant details respecting t 



nay be t 



wanting to complete the character. 



Having already noticed the true relationship of Stoma gyrinus, it necessarily 

 follows 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 SUuri, has 

 formed a distinct genus for the Sihini* nyrimtx, which he has named Schilbroilrs, and 

 which is interposed between Hemotogon/s of Girard and Trichomycterus of Cuvier and 

 Valenciennes, in the subfamily of Silurichthyoidei and the group of Trkhomyeterini. 

 Bleeker's generic characters are the following: 



