Lewisville Lake , Denton , TX
See map: Google Maps
Burrow: 43 mm x 14 mm x 9 mm; Coprolite: 1.5 mm dia x 2 to 2.5 mm long
Think of this like as a little chamber pot. This accumulation of coprolites that may drifted into an empty burrow or other hollow structure. Another possibility is that they were left by a worm dropping them in the tunnel left as it ate through its lunch.