EXPLANATION OF TERMS AND MEASUREMENTS CXX1X 



spines and soft rays in a continuous series, a comma is used to separate the numerals indi- 

 cating the two portions, "Dorsal X, 13," for example, indicating a single dorsal fin with 

 10 spines and 13 soft rays. Two separate dorsal fins are indicated by a dash separating 

 the numerals, "Dorsal X-12" and "Dorsal X-I, 12," indicating respectively: first, a single 

 spinous dorsal of 10 spines followed by a separate soft dorsal of 12 rays; and second, a spinous 

 dorsal of 10 spines followed by a separate second dorsal fin consisting of a single spine and 

 12 soft rays. 



The height of a fin is measured on the longest ray. 



The length of a fin is measured along its base. 



The origin or insertion of a fin identical terms is that of its first ray, or spine. The position 

 of a fin is, technically, the distance from the tip of the snout to the base of its first ray or 

 spine. For example, it may be said of a fish that the "position of the dorsal fin" is con- 

 tained more, or less, than twice in the fish's length 



4. THE SCALES 



The most ready indication of the size of the scales in a fish is furnished by the enumeration of 

 the scales in the lateral line, or, if that is absent, of those in a line along the horizontal axis, 

 as nearly as possible, from the upper corner of the gill-opening to the base of the caudal 

 rays. It is customary in descriptions to include also counts of the scales in oblique series 

 from the middle line of the back to the lateral line and including it; and the number between 

 the lateral line (not including it) and the median line of the belly in front of the anal fin. 

 These counts are expressed in a conventional formula, "Scales 6-42-9," for example, 

 indicating 6 scales in an oblique series above the lateral line, 42 in the lateral line (or in a 

 longitudinal series from the gill-opening to the base of the caudal rays), and 9 in oblique 

 series below the lateral line. 



9 F 



