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184 Bailey and Cross <br />per cent of the fish), from 4.7 to 3.3 per cent of the length in <br />wens of album. The fin -ray counts provide another expression ui <br />length, and since our data for these show no overlap (Table I) the <br />counts are more reliable than are the measurements. <br />Size and distribution of plates. — Although the numbers of plates <br />in the longitudinal series do not differ between the species (p. 17,5) <br />there is a pronounced difference in the height of these plat. <br />consequently in the interspace between the rows. The measui, t <br />of the tenth lateral plate (Fig. 6) varies less than that of the pace <br />between this plate and the ventral row, probably because the inter- <br />space is .0 part dependent on the condition or facness of the body. <br />In an emaciated specimen of album that had been kept for a long <br />time in an aquarium the interspace was unusually narrow, althouLh <br />t <br />a. J'' <br />• <br />J � <br />i O • <br />I = Z •S DWOtynry a <br />Z <br />W & <br />r <br />.00 200 300 4O0 SOO 500 ',- <br />STANDARDLF'. <br />FIG. 6. Scatter diagram showing proportional height of tenth lateral <br />in the species of Scaphirhynchus <br />the tenth plate was of normal size. At a body length of less than <br />200 min. the tenth lateral plate is relatively small; but in fish longer <br />than 230 mm. its height increases little if at all faster than body <br />length. In the Iarger fish a plate height equal to 3.4 per ct :: o: <br />l —'­ length provides a convenient and usually reliable line of <br />i:(Pii ­1 Lveen the species: only 1 of 13 specimens (8 per cent) of cauum <br />has a larger value (3.3 per cent) and only 2 of 30 (7 per cent) platoryn- <br />chus specimens have a smaller one (minimum 3.2 per cent). The <br />relative width of the interspace increases until a body length of at <br />least 230 mm. is attained. The data suggest some relative :r• - <br />wim growth thereafter, but individual variation is great ant: cne <br />number of available specimens longer than 400 mm. is too small to <br />furnish a conclusive test. <br />Like the plates in the primary rows, the lesser dermal ossifications <br />in platorynchus are larger, more closely spaced, and more completely <br />