GLIRES OF THE SANTA CRUZ BEDS. 485 



The measurements of limb-bones are all from No. 15,648. 



Humerus, length 062 Tibia, distal width oio 



" proximal width on Fibula, distal width 004 



" distal width 01 2 " " thickness 006 



" width of trochlea OOQS Astragalus, length 013 



Radius, proximal width 007 " width of trochlea 007 



Ulna, width at sigmoid notch 0065 " " " distal end 006 



Femur, length from head 080 Metatarsal II, length 030 



" " " great trochanter .. .084 " " proximal width 004 



" proximal width 02 1 " " distal 005 



" distal width 017 Metatarsal III, length 03 1 



Tibia, length 091 " " proximal width 0055 



" proximal width 0175 " " distal width 007 



SCHISTOMYS ROLLINSII Sp. HOV. 



(Plate LXIX, Figs. 1 8-1 8 s .) 



The type specimen (No. 15,969), an incomplete skull, was found by 

 Mr. Hatcher at Lake Pueyrredon. In size, this species equals S. ellipticus, 

 but differs in many other respects. The upper incisors which are dis- 

 played in the broken end of the rostrum, are remarkably thick; p 1 , 

 though entirely molariform, is very small and m^ has a shorter posterior 

 process than in the preceding species ; the downward inclination of the 

 grinding surfaces of the upper dental series is less marked, the face being 

 less flexed upon the cranial axis ; the cranium is more depressed and flat- 

 tened, with less antero-posterior arching ; the supraorbital border is some- 

 what raised and thickened, but not notched. The rostrum is long and 

 exceedingly broad, especially on the dorsal side, narrowing on the ventral 

 side, and the nasals are much wider than in S. ellipticus. The palate is 

 slightly less triangular than in the latter and the posterior nares are not so 

 broad and have more nearly parallel sides, being shaped more as in 

 Rocardia. 



MEASUREMENTS. 



Upper dentition, length pA-mS. 017 M-2-, length 0055 



Upper incisor, width 003 Skull, interorbital width 024 



" " thickness 0045 Palate, width at p 004 



PA, length (i. e., antero-posterior diam- " " " m^ OIO 



eter) 0025 Rostrum, width at base 015 



" width (i. e., transverse diameter). . . .003 



This species is dedicated to my friend, Philip Asheton Rollins, Esq., of 

 New York, whose interest in the work of Patagonian exploration has been 

 repeatedly and most generously displayed. 



