416 EXPLOKATIOSTS ACROSS THE GREAT BASIN OF UTAH. 



The restriction of Cuvier will exclude its application to any except those with teeth 

 only on the jaws. 



Rafinesque having conferred a name -on those species which had eight barbels, and 

 teeth on the jaws only, the name is excluded from application to any of them. 



Subsequent authors have separated other forms referred by Lacepede to the 

 genus. The only species that remained after them, which was not covered by the 

 generic characters of the species separated from Pimelodus, was the Pimelodus maculatus- 

 For that species the generic name Pimelodus must be then retained. That species has 

 been referred by Dr. Bleeker, in his recently-published monograph of the Silurii, to a 

 genus to which lie has given the name Ilhamd 'hi, and which had nearly simultaneously, 

 but probably somewhat later, received from myself the name of Pimelonotus. As the 

 Pimelodus mam/ntus appears to be generically distinct from the Pimelodus Sebce, the 

 type of the genus llhumliu. both names may still be retained. 



ICTALUBI, Gill. 



The body is more or less elongated, compressed posteriorly, and terminated by a 

 well-developed caudal tin. The skin is naked and unprovided with sucking-cups. 



The head in profile presents the appearance of a more or less elongated cone, and- 

 is covered by a skin which is generally quite thick. It is more or less flattened and 

 broad above, and gradually becomes narrowed to the convex snout. There is never 

 a casque, or helmet. The supra-occipital terminates in a point. 



There are eight barbels: the two maxillary constant in the family, a pair in front 

 of the posterior nasal apertures, and two pairs arranged in a curved line behind the 

 lower jaw. 



The nostrils term nearly a transverse parallelogram between the interniaxillaries 

 and the eyes; the anterior are suboval or subcircular, and the posterior linear, with 

 a raised margin, from the front of which the upper barbels originate. 



The eyes are generally placed in the anterior half of the head. 



The branchial apertures are ample, continued from the supero-posterior angles of 

 the opercula to beneath the throat. 



ICTALUKUS, (Raf.) Gill. 

 Synonymy. 



Ictaltjrus Raf. Ichthyologia Obiensis, p. 61. 



Elliops Raf. Ichthyologia Ohiensis, p. 62. 



SYNKCHOCrLAXis Gill, Annals L N eeum of Nat, Hist, of New York, vol. VII, p. 39. 



riMELODCS sp. Kirtland, and. 



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

 but slender, and presents behind the anal an elongated elliptical section. 



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

 ward and outward. The supra-occipital 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 lateral. 



Mouth moderate or small, transverse, and terminal. The upper jaw generally 

 protrudes beyond the lower. 



