class="id2">Sand

..... 00.7   ..... ..... ..... ..... Pharyngeal tooth ..... 00.3 ..... ..... ..... ..... ..... Total (%) 100.0 99.8 100.0 100.0 100.0 100.0 100.0

Spawning apparently occurs when river levels recede to the seasonal lows. In late summer, temperatures of these rivers probably are maximal, their turbidities are reduced, and their sandy bottoms are stable. Underhill (1959) reports that this species is rare in the Vermillion River, a northeastern tributary of the Missouri River, except in autumn when large numbers occur near the mouth of the river. We suspect that this is associated with spawning.

PLATE 21