342 



DIPODOMYS. 



incisors, acuminate; zygomata delicate, straight, abutting against 

 tympanics, which are greatly inflated and possess a nontubular 

 orifice of meatus; mastoids enormous; squamosals reduced; parietal 

 triangle-shaped; interparietal small, situated between forks of occip- 

 ital; bullae in contact below the basisphenoid ; palate terminating 

 posteriorly with a sharp median somewhat lengthened spur; external 

 to this is a fossa with two small anterior foramina, and a large one 

 behind pterygoids, with a hamular termination abutting the bullae; 

 basioccipital narrow, acuminate, reduced, separated by a fissure for 

 its entire length from the bullae; a similar fissure divides the last 

 named bones from the alisphenoid and squamosal. The interorbital 

 foramen is placed low down, midway on the side of the rostrum; 

 incisive foramina minute slits between incisors and molars. In the 

 rear of the skull the occipital bones appear as a rim to the foramen 

 magnum; upper incisors sulcate, pointing backward; molars rootless; 

 mandible small, thick, with a conspicuous acute lamina twisting 

 obliquely outward and upward; mental foramen outside, near incisors; 

 hind legs elongate; tail longer than head and body, penicillate; soles 



FIG. 65. DIPODOMYS PHILLIPSI. 



No. 5913 Am. Mus. Nat. Hist. Coll. Nat. size. 



UPPER TOOTH ROW. LOWER TOOTH ROW. 



Enlarged 7 times. Enlarged 7 times. 



