Fictitious and Symbolic Creatures in Art, by John Vinycomb, [1909], at sacred-texts.com

p. 217

Musimon, Tityrus

A fictitious animal mentioned by Guillim and others. It nearly resembles a goat, with the head and horns of a ram, but has besides the horns of that beast, a pair of goat's horns. It is also mentioned in Guillim's "Display," where it is said to be a bigenerous beast, of unkindly procreation, engendered between a goat and a ram, like the Tityrus, the offspring of a sheep and goat, as noted by Upton.