CATFISH GENUS NOTURUS RAFINESQUE 5 



Methods 



Descriptions of most of the counts and measurements used in this 

 study can be found in Hubbs and Lagler (1947, pp. 8-15 and later 

 editions). The counts of caudal rays and pores in the sensory canal 

 system and some measurements are especially applicable to these 

 fishes. They are not generally used or have been employed in this 

 group for the first time. 



Counts 



Anal fin rays. — All rudimentary rays at the anterior end of the 

 fin were counted. These simple rays decrease somewhat in number 

 with age, i.e., some become branched rays. The number of anal rays 

 was usually determined by making an incision above the anterior end 

 of the fin, along the side of the body, then pulling the skin down to 

 expose the minute rays, and counting them with the aid of strong 

 transmitted light. A few counts were obtained by use of soft x-rays 

 (see caudal fin rays). The full number of anal rays is present and 

 countable at a very early age. 



Dorsal fin rays. — Except in Prietella a prominent long hard spine 

 is always present at the anterior end of the dorsal fin and is preceded 

 by a short plate-like spine; neither is usually indicated, because the 

 variation is in the number of soft rays. The full complement of dorsal 

 fin rays is present in the yolk sac stage. 



Pelvic and pectoral fin rays. — A hard spine always precedes the 

 soft rays of the pectoral fin, but it is also usually excluded from the 

 tabulations. The outer pelvic ray is typically simple, but on occasion 

 may be branched; the frequency of occurrence of its branching was 

 not determined. A minute ray-like structure, separate from and lateral 

 to the base of the outer pelvic ray, was observed in Ictalurus and 

 Pylodictis after clearing and staining. This structure has apparently 

 degenerated into a small round ball or disappeared in Noturus. 

 Shelden (1937) did not mention the element; if it is a degenerated ray 

 or an accessory structure is not known. It is not included in the fin 

 ray counts. 



Enumerations from both the right and left fins are tabulated. In the 

 genus Noturus, nothing is gained by adding the counts from the two 

 sides. Individual asymmetry is frequent, but no population was found 

 to be predominately asymmetrical. A slight suggestion of correlation 

 in the increase in numbers of both pelvic and pectoral fin rays was 

 noted in several species, particularly in N. jlavus, N. albater, N. 

 eleutherus, N. miurus, N. gyrinus, N. nocturnus, N. gilberti, N. phaeus, 

 and A^. funebris. In them, a high number of pectoral rays is frequently 

 accompanied by an increase in number of rays in the pelvic fin. In 



