Captain Thomas LEWELLEN - Lewellen (as he invariably signed himself) originally joined Captain Henry Augustine's company, recruited from around St. Augustine, Texas, and became its commander during the fighting at Bexar. In the reorganization of the army that followed the end of the siege he was named commander of a new infantry company seemingly formed by combining the remains of the various Texas companies with the surviving members of Captain John Peacock's United States Invincibles, an American volunteer company from Mississippi. In January he marched with Grant to Goliad and at Refugio elected to follow him to San Patricio and down to the Rio Grande. The captain and his company were closely assoicated with grant in the operations thay followed, and Lewellen died with most of them at Agua Dulce.
Source: The Secret War for Texas, by Stuart Reid, pub. Texas A&M University Press, 2007