Both maxillary bones are incomplete, and lack the zygomatic processes. The rostral part of the maxillary is compressed laterally, as is the premaxillary. The anterior border of the maxillary contributes to the formation of the border of the anterior opening of the infraorbital canal where, at the posteroventral border of the opening, the bone is produced into a prominent tuberosity which projects laterally approximately one millimeter on each side. The infraorbital foramen (anterior opening of the infraorbital canal) lies about midway between the anterior end of the skull and the root of the zygoma. High on each side of the rostrum, and beneath the dorsal edge of the masseteric plate, is an area containing small foramina. The zygomasseteric plate is inclined forward at the dorsal end, and extends anteriorly almost to the highest part of the arch of the canal for the root of the incisor. The posterior end of the infraorbital canal lies on the median side of the zygomatic root as it does in _H. hatcheri_ Wood. Ventrally the zygomatic root rises above the fourth premolar as in _H. gregoryi_ Wood, _H. hatcheri_, and in Recent heteromyids. The ventral part of the orbit, containing the sphenopalatine foramen, presphenoid foramen, and the sphenoidal fissure, is not constricted as in _Liomys_, but is open like that of the squirrels. This condition is emphasized by the narrowness of the interorbital part of the skull and the more vertical position of the orbital plate. The alisphenoid bone is large and forms part of the posteromedial wall of the orbit. The sphenofrontal foramen lies in the suture between the extreme anterior margin of this bone and the frontal bone. The orbitosphenoid bone makes up little of the orbital wall. It occupies the posterior area of the orbit between the alisphenoid and palatine, and is in contact with these bones and the frontal. The presphenoid canal between the orbits is large, and the entrance at each end is well separated from the sphenoidal fissure. Damage to the sphenoidal fissure, which occurred prior to preservation, obscures its relationship to the optic foramen. No bar was found that would indicate that the two openings were widely separate. Anteroventrally the sphenoidal fissure is bounded by the orbitosphenoid bone, and dorsolaterally by the alisphenoid bone. Between the presphenoid foramen and the orbitosphenoid-frontal suture there is a distinct ridge, and the suture between the two bones lies in an elongate pit or trough formed by the anterior sloping side of the ridge and the impressed lateral wall of the frontal bone.