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Sturgeons of the Genus Scaphirhynchus 1.7 <br />and anal counts there is no recorded overlap between the species; <br />in the paired fins the differences, though significant, are subject to <br />enough overlap to limit their value for identification. <br />_llorphametry <br />` measurements taken on 16 individuals of Scaphirhynchus <br />and on all but two (15) of the available specimens of S. <br />album are expressed as thousandths of the standard length in Tables <br />II and III. Fork lengths are recorded to permit conversion of the <br />data to that base measurement. For 21 measurements, differences <br />between the species either are nonexistent or are so slight as to lack <br />--ol in identification. That the species differ significantly- 1',1 <br />iieasurements is obvious not only from the data but, with <br />from direct visual comparison of the fisii. Some dif- <br />ferences apply only to specimens of like size, and others are in part <br />obscured by overlap resulting from individual variation. \o geo- <br />graphic variation is apparent. Stud- of geographic variation, how- <br />ever. has not been a prime function of this inquiry, and <br />cimens of S. album from Louisiana and for single examples of <br />.Iatorynchus from the Ohio and Mississippi rivers, all measured <br />r. �.,me from the _Missouri River drainage. Future comparison of <br />adequate material may reveal geographic variation. <br />In order to appraise ontogenetic changes and individua; <br />while making interspecific comparisons, graphs of proportional meas- <br />u — -nents against body- length were made for each of 14 characters. <br />cedure indicated the desirability- of more data. so 11 measure - <br />n. _L ,Nciv made on each of 38 additional specimens of Scc`?hirhrtn- <br />chus plator'?mchus. <br />(lead length. —In small specimens the head is proportionate) <br />rge, and its ic•ngth rs probably not sufficiently distinctive to permit <br />reliable specific identification until a standard length of about 200 <br />attained. In larger fish the head length of 92 per cent (11 of <br />i 11e specimens of album is at least 30.5 per cent of the standard <br />length; the head length of 96 per cent. (45 of 47.) of platorynchus <br />specimens is shorter ( Fig. 1). <br />Snout length and rostral length. — Rostral length is esscutialll- an <br />alternative expression of snout length, and since both measurements <br />shoe- the same growth histor'- and specific differences onl"• suout <br />length is discussed here. The snout in album is more pointed (Fig. 2) <br />