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 

 unkvlosed 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 



FIG. 63. ZYGOGEOMYS TRICHOPUS. 

 No. 50107 U. S. Nat. Mus. Coll. Nat. size. 



