This fossil is a horn coral called Siphonophrentis elongata (Rafenesque & Clifford, 1820). It was found in the Jeffersonville Limestone of Jefferson County Kentucky USA. The creature lived in the Middle Devonian Period. This species of horn coral was one of the largest that ever existed. Since it is, the fossil is pretty easy to identify when it is found. They are hard to find fully intact though. The maximum length can get to 60-80 cm and its largest diameter 8-10 cm.
This fossil was first described as Turbinolia buceros var. elongata by C.S. Rafinesque and J.D. Clifford in the 1820 article, Prodrome d' une monographie des Turbinolies fossils du Kentucky (dans l' Amerique Septentrionale) found in Annales Generales des Scinces Physiques [Bruxelles] Tome V, pages 231-235. The fossil was renamed by Erwin C. Stumm in the 1949 paper Revision of the families and genera of the Devonian tetracorals in Geological Society of America Memoir 40, 92 p., 25 Pls.
Below is a digitally altered image of Rafinesque taken from the book The Life and Writings of Rafinesque by Richard Ellsworth Call, Filson Club Publications No. 19, Louisville Kentucky printed by John P. Morton and Company 1895. The image was from a painting by Jouett in the Wisconsin Historical Society collection courtesy of Honorable R. G. Thwaites, the Secretary. The portrait painter Matthew Harris Jouett (1788-1827) was born and died in Kentucky.
This fossil has a special significance in relation to the Commonwealth of Kentucky. It was first described by one of Kentucky's first scientist/naturalist Constantine Samuel Rafinesque (1783-1840). He was born and self-educated in Europe. Between 1819-1826 he taught at Transylvania University in Lexington, Kentucky. While there, he published a number of works with a local merchant John D. Clifford (1778-1820). Using the book about Rafinesque mentioned above as source, Clifford was responsible for Rafinesque teaching in Kentucky and if he had not died suddenly would have more than likely continued to co-author more works on natural science.
Their 1820 article was the first to describe some of the coral fossils from the Falls of the Ohio in which they described over 34 species. The descriptions are incomplete and without illustrations though. None of their types were located by Erwin C. Stumm in the 1964 definitive work on Louisville area corals entitled Silurian and Devonian Corals of the Falls of the Ohio published in The Geological Society of American Memoir 93 page 5. He did note that the coral fossil now known as Siphonophrentis elongata was referred by them as "petrified Buffalo horns" and was also named by the French naturalist Charles-Alexandre Lesueur as Zaphrentis gigantea.
The genus Siphonophrentis was named by Majorie O'Connell in the Revision of the Genus Zaphrentis in Annuals of New York Academy Science Volume XXIII. pp. 177-192, February 25, 1914. [LINK]