Fusulinids lived in great abundance along the margins of the Late Pennsylvanian seas of northcentral, central, and western Texas on shallow carbonate or clastic depositional shelves and were scarce or absent below the edge of these shelves in the deeper water "starved" basins. These shelves were populated by twelve species lineages of Triticites Girty and Dunbarinella Thompson. Some elongate species of Triticites are closely associated with sediments of impure silty limestone and fine to medium sandstone that indicate shallow interdistributary bays, lagoons, and wave-built bars and terraces. Many large fusiform specimens of Triticites are associated with shallow water algal meadows, banks of crinoidal fragments, and coarse calcarenite which suggest an environment similar to that in Recent Florida Bay. Small fusiform representatives of Triticites are most common in poorly sorted limestones that were probably deposited in slightly deeper water on the shelves that extended down to effective wave base. Some morphological changes in the several evolving lineages were adaptive and functional and include such features as thickening of the wall, greater folding of septa, and addition of heavy internal coatings of secondary deposits that increased strength and stability of the shell. Shell shape may also have had a functional purpose. These Late Pennsylvanian fusulinids lived on the surface of the substrata and were primarily sensitive to physical and chemical ecological features of bottom currents, waves, and associated organisms.