1899.] NATURAL SCIENCES OF PHILADELPHIA. 297 



Cauda or 3/. cricetulm. Nasal branches of premaxillaries narrow, 

 scarcely reaching posterior edge of nasals. Mandible larger than 

 in M. cricetulus, but with much more slender angular process. 



Measurements of type skull : greatest length, 28 ; basal length, 

 27; basilar length, 25.4; zygomatic breadth, 16.4; mastoid 

 breadth, 13; interorbital constriction, 5 ; length of nasals, 8.8; 

 anterior breadth across nasals, 3.8; posterior breadth across nasals, 

 2; diastema, 8.8; palatal length, 14; occipital depth, 8.4; 

 fronto -palatal depth (at middle of molar series), 7.4; mandible, 

 18; maxillary toothrow (alveoli), 7; mandibular toothrow (alve- 

 oh), 6.8. 



Teeth. — Incisors pale yellow as in 31. cricetulus. Molars much 

 heavier than in M. cricetulus, but enamel pattern exactly similar.^ 

 The salient angles are, however, less acute, and the terminal loop 

 of the posterior upper molar forms less than half of the length of 

 the tooth crown instead of slightly more than half as in M. albi- 

 cauda and 31. cricetulm. 



Specimem examined. — Dr. Abbott took only one specimen of 

 Microtia acrophilus. On the label he writes: " Vast numbers 

 inhabit the cliff of conglomerate at sides of the nullah, issuing 

 forth at evening. Country absolutely destitute of vegetation." 



Remarks. — This species is closely related to 3Iicrotus stoliczkanus, 

 but is readily distinguishable by its short tail and very pallid color. 



3Ieamrements. — The measurements of the t}^)e of 3Iicrotv.i 

 acrofhilus are given in the accompanying table: 



' The front lower molar in each jaw is imperfect anteriorly. 



