614 



MONOGUArUS OF NORTH AMERICAN KODENTIA. 



on the outer side, a fine ridge, vvbicb marks off a secondary groove within the 

 fust. The same thing occurs in the single-grooved species — castanops, mexi- 

 canus, and hispidus. But this carination of the main groove is not always 

 perceptible, and is generally so fine as to be liable to be overlooked. When 

 most strongly marked, this supplementary groove is just like the inner marginal 

 groove itself; and each tooth then seems to consist of two similar halves.. 



Table I. — Measurements of forty specimens, fresh and alcoholic, of Geomys bursarius. 



* A type of breviceps. 



i Xns. 1-42 (nri^ DOS.) were measured in the flesh by the collector, Dr. C. E. McCuosney.'U. S. A., whose caro in this 

 mat ti i greatly Increased the value of an important collection of Mammals made by him in the- locality named. " Fort Sis- 

 seton" was formerly Fort Wadaworth, Dakota. 



