The hyoid apparatus of the squirrel, Funambulus consists of basihyal, the immovably fused posterior cornu represented by thyrohyal and the long slender and flexible anterior cornu which is divisible into hypohyal, caratohyal, stylohyal and tympanostyloid synchrondosis. Since the stylomastoid foramen lies posterolateral to the distal tip of the anterior cornu, the hyoid is of the protrematic type. The hyoid apparatus of Funambulus palmarum differs from that of Funambulus pennanti in minor but well marked characters such as a less arched basihyal with smooth shoulders, a small entoglossal process, a trochanter on the lateral side of thyrohyal, a longer hypohyal and a shorter ceratohyal.
All the muscles which originate or insert on the hyoid skeleton and their innervation are described. The muscle digastricus of the squirrels is quite characteristic with a well marked intermediate tendon between the anterior and posterior bellies. The muscle jugulohyoideus originates from the paraoccipital process and is well developed, but the stylohyoideus is slender, foreshadowing the condition in gerbils in which only one of these two muscles, possibly the jugulohyoideus is represented.