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180 Bailey and Cross <br />Job _ <br />♦ • <br />J n 50 • • • I •i • •♦ <br />• • • • <br />W o 28l— • • V. • <br />_ • •• • <br />u 26F • • ♦5 aAtn <br />g 251'-' • •S pplorynpyt '� <br />W 200 300 •OD 500 600,p <br />STANDARD LENGTH ,Mm) <br />FIG. 1. Scatter diagram showing proportional length of head in the <br />species of Scaphirhynchus <br />and longer than it is in platorynchus. Although few large adults of <br />either species have been measured, the difference seems to increa,e <br />with age. In fish less than 300 mm. long the snout lengths are suffi- <br />cientl• alike to preclude positive identification, and in a few speci- <br />mens of platorynchus between 300 mm. and 400 mm. long the snout <br />is quite as sharp and as long as in some examples of album. ut <br />above 300 min., the snout of 10 (91 per cent) of 11 specimen - <br />.5can7,irh7tnchus album is at least 17.4 per cent of the standard <br />2 a 2,.' ' ♦ I I ♦ ♦S czm <br />9 1 j� • ♦ ♦ • ♦ ♦ •S p.oruyncsY� <br />O P;Sr • • • • _. <br />i I <br />_0 200 300 400 500 a70 <br />STANDARD LENGTH (NM) <br />FIG. 2. Scatter diagram showing proportional length of snout in the <br />species of Scaphirhynchua <br />and I he snout of 23 (93 per cent) of 27 examples of S. platorynclizis is <br />no more than 16.9 per cent of the length. <br />Orbit length. —In both species the eye is minute, but it is -iv <br />lai-er in young fish, becoming smaller with age until a length of about <br />230 mm. is attained. As a corollary- of the high turbidity- of the <br />waters to which album is restricted, the eye in this species is smaller <br />(usually 0.9 to L2 per cent of standard length) than in platorynchus <br />(typically 1.2 to 1.5 per cent), which often occurs in raters of moder- <br />ate turbidity-. Individual variation, however, is considerable jah', -S <br />II and III), and this character by itself is not trustworthy for identi- <br />fication. <br />