Introduction. lvii 



ing the objects used for food in pieces which will -admit of being swal- 

 lowed. 



The fins of fishes are composed of spines and rays, the former 

 being stiff, bony structures usually connected by a thin membrane; 

 the rays are rather weak, jointed cartilaginous structures and are also 

 connected by a thin membrane. Spines are present on one or more 

 fins of all of the spiny rayed fishes. The dorsal and the pectoral fins 

 of some of the soft rayed fishes, as the Carp and the Catfishes, are 

 preceded by a spine which is only the modification of one or more of 

 the soft rays. Most fishes, except Catfishes, are covered with scales. 

 A cycloid scale has its posterior margin smooth; such scales are 

 usually found on soft rayed fishes. A ctenoid scale has its posterior 

 margin rough or toothed; such scales are characteristic of the spiny 

 rayed fishes. 



The length of the fish is measured from the tip of the upper jaw 

 to the base of the caudal fin or end of last vertebra, the total length 

 from extreme ends of the fish. The length of the head is measured 

 from tip of upper jaw to the posterior edge of the opercle, the length 

 of snout from tip of upper jaw to anterior margin of the orbit. The 

 depth of the body is measured at its deepest part, none of the fins 

 being included; the depth of caudal peduncle is measured at its 

 narrowest part, its length from base of last anal ray to end of last 

 vertebra. Only fully developed fin rays are counted, the rudimentary 

 dorsal and anal rays when closely adnate to the first ray is counted 

 as one; when the last ray is double and the two parts have the same 

 base it is counted as one ray. The scales in the lateral series are 

 counted from upper edge of opercle to base of caudal fin, the trans- 

 verse series from the dorsal fin to ventrals or origin of anal, which- 

 ever is nearest the middle of the body. In making the transverse 

 count the scale on the lateral line, when it is present, is counted with 

 those on upper part of body. The length of the dorsal and anal 

 fins is measured along their bases, the height is the length of their 

 spines or rays. The length of the other fins is measured from attach- 

 ment to the body to the tips of longest rays. 



Substantially the same order is followed in all descriptions. The 

 comparative measurements which best indicate the general form of 

 the fish are given first; the number of spines and rays of the dorsal 

 and anal fins next, and the number of scales in the lateral and trans- 

 verse series last. These are followed by a general remark on the form 

 of the fish, and then other important specific points are given in detail. 

 The description of the color is given last. 



In order to abbreviate, the following expressions are used: "Head 



