266 ERETHIZON. OCHOTONA. 



b.— myops. {Enthrhon), Merr. , Proc. Wash. Acad. Scien., igoo, p. 27. 



Type locality. Portage Bay, Alaska Peninsula. 



Genl. Char. Similar to E. epixanthus ; tail and hind feet shorter; 

 face whiter; zygomata bowed outward, outer side convex; breadth 

 between squamosal anteriorly, greater than that of occiput; outer 

 wall of anteorbital vacuity straight, vertical. 



Color. Similar to E. epixanthus, but flanks and sides of tail more 

 yellow and fore part of head grayish. 



Measurements. Total length, 630. 



Fam. IX. Ochotonidae. 



Form arvicoline; limbs subequal; external tail wanting. Skull 

 flat, depressed; no postorbital processes; molars rootless; clavicles 

 well developed. 



68. Ochotona. 



I. i=i; P. ?="; M. 2=^ = 24. 

 i-i' 2—2' 3—3 ^ 



Ochotona. Link, Beitr. Nat., 1795, 11, p. 74. 



Lagomys. Cuv. Regn. Anim., 1817, i, p. 219. 



Ogotoma. Gray, Ann. Mag. Nat. Hist., 1867, xx, p. 220. 



Superior outline of skull arched, occipital region only slightly 

 depressed; postorbital processes wanting, and the paroccipital pro- 

 cesses undeveloped; malar prolonged almost to auditory opening; 

 orbits open upwards, placing the zygomata on a higher level; occi- 

 pital plane perpendicular, foramen magnum very large; audital bullae 

 greatly developed and extending backward to level of occipital plane; 

 pterygoid fossa broad and deep, narrowing posteriorly; vomer joins 

 basisphenoid; palate wider than long, merely a narrow bridge ter- 

 minating posteriorly in a rounded arch. Skull above broad pos- 

 teriorly with a slight sagittal crest, narrowing anteriorly; anteorbital 

 constriction considerable; nasals extending backwards to orbits, trun- 

 cated posteriorly, widest anteriorly. Condyloid part of under jaw 

 broad, quadrate, and slopes but little backward; coronoid process is 

 a mere tubercle, and there is a second smaller tubercle near last 

 molar. Mental foramen situated nearly opposite middle molar 

 instead of being in fore part of jaw. Upper incisor broad, long and 

 with a deep groove on outer side, dividing each tooth into unequal 

 halves, and terminating in two points, the cutting edge being deeply 

 notched and gauge-shaped instead of chisel-shaped. Lower molars 

 are deeply grooved on the sides, causing the salient angles to be very 

 prominent; first molar has two grooves on outer surface; last molar 



