ZYGOGEOMYS. 331] 
Skull long and narrow; maxillary and squamosal branches of 
zygoma in-contact above jugal, which is mainly external; rostrum 
long and narrow; orbitosphenoids large, and with the exception of 
a foramen at apex, close the upper part of sphenoidal fissure, and 
ankylosed with the alisphenoid; mesethmoid quadrangular; upper 
incisors bisulcate, chief sulcus on median line, minor on inner con- 
vexity. First and second upper molars with two enamel plates 
Fic. 63. ZYGOGEOMYS TRICHOPUS. 
No. So1o7 U.S. Nat. Mus. Col]. Nat. size. 
