THE CATFISH. IOI 



or pelvic fins are attached. Compare with some small scale fish 

 in which the pelvic fins are so far forward as to be beneath the 

 pectoral. 



g) Spread the fins, one at a time, and count the fin rays in each. 

 Examine with a lens and note that all the rays are jointed like the 

 antennae of a crayfish and that they bifurcate one or more times. 

 The web of the fin is simply a sharp fold of skin enclosing the rays. 

 Are the latter connected in any way with the endoskeleton ? 

 Satisfy yourself on this point by cutting down into the flesh on the 

 right side of the dorsal fin. How many of the fins are provided 

 with a stout spine ? What purpose do these spines serve ? 



h) About the snout are a number of long, projecting filaments, the 

 barbels. Count them. The largest pair, at the corners of the 

 wide mouth, are the maxillary barbels. Move one of the latter 

 about and note that it is attached to a short cylindrical bone, the 

 maxilla. This bone is better developed in the common scale 

 fishes. Is there any probable connection between the name 

 "catfish" and the presence of these barbels? What is their 

 function ? 



i) It will be noted that the eyes have no lids and that there are no 

 external evidences of the ears. Determine the number and 

 position of the nostrils. Probe them to see what connection they 

 may have with one another. Do you find any opening from the 

 nostrils into the mouth ? 



j) The mouth is terminal in the catfishes. Compare with a sucker in 

 this respect. Look for the teeth, which are located on pads at 

 several places. The two pads just inside the upper lip are borne 

 on the premaxillary bones. Are the latter united in the median 

 line ? Similarly situated on the dentary bones of the lower jaw, 

 or mandible, are the mandibular teeth. Rub the tip of your 

 ringer over them to see which way they project. 



k) Elevate the tongue by pressing down with the thumb on the man- 

 dibular pads of teeth and upward with the fingers on the under 

 side of the lower jaw. Has the tongue much freedom of move- 

 ment ? 



