Article IX. THE EXTERNAL EAR BONE IN CERTAIN 



RODENTS. 



By J. A. ALLEN. 



My attention was recently called by my assistant, Mr. F. 

 A. Schneider, to a skull of Liomys canus Merriam which 

 showed a singular bony appendage attached by a ligamentous 

 hinge to the front lower border of the left meatus auditorius, 

 it having attracted his notice, in cleaning the skull, as some- 

 thing out of the ordinary. As he had several other skulls of 

 this species to prepare, I urged him to take great care to save 

 this appendage in situ. As a result he found it on one or both 

 sides of several of the remaining skulls, including the one here 

 figured. 



This external ear bone is situated at the front lower border 

 of the meatus and is hinged to it by ligament ; it has the 



Skull of Liomys camis^ Merriam, showing external ear bones. No. 20995, Am. Mus. Nat. 

 Hist., 3 ad. Twice nat. size. 



form of a truncated oval or crescentic appendage, quite large 

 and prominent, as shown in the accompanying figures. Al- 

 though hinged and moveable, the range of movement is from 



