420 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



(standard length). For conversion to standard 

 length the following formulas apply: 



„, , , , ,, fork length — 

 Standard length= ^ a; 



total length — 



standard length = 



The following a and 6 values were obtained : 



crysos 



Fork length: = 0.947,6=1.077 



Total length (less than 85 mm. standard length and 104 



mm. total length): o = -0.228, 6=1.224 

 Total length (more than 85 mm. standard length and 

 104 mm. total length): o = -4.879, 6=1.280 

 ruber 



Fork length: o = 1.020, 6=1.078 

 Total length: o = -0.896, 6=1.251 

 bartholomaei 



Fork length: a= 1.260, 6=1.073 



Total length (less than 50 mm. standard length and 61 



mm. total length) : = 0.151,6=1.219 

 Total length (more than 50 mm. standard length and 

 61 mm. total length): o= -2.609, 6=1.267 

 lahts 



Fork length: o=1.242, 6=1.082 

 Total length: o= -2.671, 6= 1.275 

 hippos 



Fork length: 0=1.006,6=1.076 



Total length (less than 50 mm. standard length and 60 



mm. total length): a = 0.326, 6=1.198 

 Total length (more than 50 mm. standard length and 60 

 mm. total length): o= -2.936, 6=1.272 



Body lengths given by workers in total length 

 and fork length and converted to standard length 

 are designated in the following manner: "about x 

 mm. (converted)." 



DORSAL AND ANAL SPINES 



Counts and descriptions. — The usual number of 

 dorsal spines is nine — eight comprise the first 

 dorsal fin, and the ninth is the first element of the 

 second dorsal fin. In the few specimens which 

 had only 6 or 7 spines in the first dorsal fin, the 

 base or position of the missing spine or spines 

 could usually be determined. On specimens of 

 hippos larger than 200 mm., the first dorsal spine 

 is relatively small and partially overgrown by 

 skin. 



A procumbent or recumbent dorsal spine in 

 advance of the first dorsal-fin spines has been 

 mentioned or tabulated in the dorsal-spine count 

 by many authors (Nichols, 1912: 185; Fowler, 

 1941a: 85; Roxas and Agco, 1941: 39; Weber and 



de Beaufort, 1931; and others). This is not an 

 articulated dorsal spine, but is shown on cleared 

 and stained specimens of the five common species 

 to be a pointed, forward extension of the first 

 pterygiophore (the third or fourth interneural 

 spine). It is more pronounced on smaller speci- 

 mens and is discernible in figures 69 to 71 and 

 81 to 83. 



There are three anal spines — the first and second 

 remain in close proximity and become appreciably 

 separated from the third with an increase in body 

 size. The third spine has a positional relation to 

 the anal soft-rays identical to that of the last 

 dorsal spine to the dorsal soft-rays. The last 

 dorsal spine and the third anal spine have been 

 ignored or incorporated in the soft-ray counts by 

 many authors. 



Lengths. — The spines were measured in an 

 erected position (if possible, otherwise estimated) 

 on a chord from the anterior points of emergence 

 from the skin to the tips. 



DORSAL AND ANAL SOFT-RAYS 



Definition. — In the early larvae, those rays 

 which from their position in the second dorsal 

 or the anal fin were considered as potentially 

 segmented were counted as soft-rays. 



Counts. — The buds or the bases of the soft-rays 

 are readily visible with magnification and trans- 

 mitted light in specimens from 8 mm. to more 

 than 100 mm. standard length. Occasionally, 

 malformed dorsal and anal fin-ray elements and 

 missing rays were encountered — these are dis- 

 cussed under Comparison of Species, page 428. 

 Malformed rays were enumerated in the total 

 soft-ray counts. Counts for fins with missing 

 soft-rays, indicated by a ray base without a ray, 

 or by an abnormally wide space between any two 

 rays, were not included in establishing ranges. 



Tabulations showing the relation of number of 

 dorsal soft-rays to number of anal soft-rays are 

 used because their numbers are apparently intra- 

 specifically correlated. 



Lengths. — Measurements were made as for the 

 dorsal spines, except on laiger specimens that had 

 developed the fleshy, scale-covered sheath along 

 the base of the fin — in which instance the proximal 

 point of measurement was taken at the emergence 

 of the erected ray from above this sheath. 



