45 



Amiurus obesus Gill. 



The head forms a quarter of the total length, and its greatest width 

 equals a fifth. Eyes small, the diameter only equal to about an 

 eighth of the head's length. Maxillary barbels extending little be- 

 yond the bases of the pectorals ; the nasal extend beyond the pos- 

 terior borders of the eyes; the external inframaxillary are little 

 longer than the internal, and equal in length the interorbital space. 

 There are nine branchiostegal rays, enveloped in a thick membrane. 

 The dorsal fin commences slightly behind the beginning of the second 

 third of the total length. The length of the anal fin equals a seventh 

 of the total. The spiniform process of the coracoid bone, from the 

 base of the pectoral spine to its tip, equals seven ninths of the spine's 

 length. The truncated caudal fin forms fifteen hundredths (15-100) 

 of the total length. 



D. 1-41; A. 171 (4.13i) ; C. 7, 1.15, 1.9 ; P. 1-8; V. 1.-7. 



The color is olivaceous above, and whitish on the abdomen ; bases 

 of the anal and caudal fins reddish. The teeth are of a dark pur- 

 plish color. 



Two specimens were collected by Mr. McCarthy, on Captain 

 Simpson's Expedition. They are supposed to have been obtained in 

 Nebraska. 



Genus Noturus Raf. 



Representatives of this genus have been described from three 

 quite different sections of the United States, and appear to belong to 

 three different species. The following is a list of them : — 



Noturus flavus i?nr/.=Noturus luteus J?ff/.=Pimelodus fla\'us 

 (young), Dekaij, Bleeker=l^oi\XY\\s flavus Kirtland, Storer. 



Noturus gyrinus itq/'.=Silurus gyrinus il/<Vc/«7/=Schilbeodes gyri- 

 nus Bleeker. 



Noturus lemniscatus 6''<ra?Y/=Pimelodus lemniscatus Les.^ Dekay, 

 VaL, Storer. 



Noturus occidentalis Gill. 



The head enters less than four times (23-100) into the total length ; 

 its greatest breadth equals a fifth of the total length. The eyes are 

 small, a diameter not exceeding a seventh of the head's length; the in- 

 terocular area equals a tenth of the entire length. Maxillary barbels 

 scarcely reaching to the bases of the pectoral fins ; nasal extending 

 slightly behind the eyes ; the external inframaxillary equal a tenth 

 of the total length, and the internal are about six or seven tenths as 

 long as the external. Nine branchiostegal rays are concealed in the 

 thick membrane. The dorsal commences with the third tenth of the 

 total length. Adipose fin arising nearly over the sixth or seventh ray 

 of the anal fin, and in the specimen described separated from acces- 

 sory rays by a naked interval. Anal fin nearly equal in length to a 

 sixth of the total. The coracoid spine is short, stout, and oblique. 



