DEC. 28, 1916. FISHES OF PANAMA MEEK AND HILDEBRAND. 235 



Unless there were not enough specimens at hand, not fewer than ten 

 were measured, and in many instances where the measurements were 

 of special importance a much larger series was used, selecting as a rule 

 as wide a range in ske as possible. The counts of fin rays, scales, etc., 

 are based upon similar series. 



Such an expression as the following, occurring at the beginning of 

 the description of nearly every species, "Head 2 to 3.5; depth 3 to 3.8," 

 signifies that the length of the head, measured from the end of the snout 

 to the bony margin of the opercle, is contained 2 to 3.5 times and that 

 the greatest depth of the body is contained 3 to 3.8 times in the length 

 of the body from the end of the snout to the base of the caudal fin. In 

 giving the number of fin rays Arabic numerals are used to indicate the 

 number of soft rays and Roman numerals the number of spines. For 

 example, D. IV-I, 16 signifies that in this instance there are two dorsal 

 fins, the first being composed of four spines and the second of one spine 

 and sixteen soft rays. If these spines and soft rays were included in a 

 single fin instead of in two fins, the result would be written thus; D. V, 16. 



For the purpose of ready identification artificial keys to the families, 

 genera and species are introduced. In using them, first determine which 

 of the major groups the species is in and then take up the regular order 

 of letters under each group. If the characters of the specimen in hand 

 do not agree with those given under the single letter, look under the 

 same double letters, ignoring all intervening matter. 



