Horn corals came in many different sizes. Small horn corals can be found in rocks of Ordovician, Silurian, Devonian, Mississippian, and less commonly in Pennsylvanian strata in Kentucky.

Enallophrentis corals are common in Devonian-age limestones. They range in size from 3 to 7 cm. Enallophrentis inflata (Hall) is outwardly similar to another small horn coral called Zaphrentis, which also occurs in Devonian-age limestones. You can tell the two corals apart by looking at the grooves (called septa) within the coral calyx (the cup). The septa are where the coral animals (polyps) attached when the corals were alive. Enallophrentis has smooth septa, while Zaphrentis has jagged septa (from Greb et al., 1993, Fig. 13a-b).

	Another example of a rugose coral. The orange color of the specimen is caused by mineralization. The limestone in which the fossil originally formed has been replaced by silica (quartz). Found in the Louisville area and donated to the Kentucky Geological Survey by R. Todd Hendricks.
	Another example of Enallophrentis inflata, a type of rugose coral. Found in the Louisville area and donated to the Kentucky Geological Survey by R. Todd Hendricks. All Enallophrentis identifications by Alan Goldstein

Rugose corals can be found in the basal parts of some dark gray shales of Pennsylvanian strata in both of Kentucky's coal fields. This Lophophyllidium specimen is 3 cm long and was collected in the Kendrick Shale Member in eastern Kentucky.