42 BULLETIN 43, UNITED STATES NATIONAL MUSEUM. 



notes 1 have carefully soaked oue of the skius in diluted spirits and 

 liave detected tUat the apparent mutilations of the auricle are due to 

 distortion, and that the form of the auricle is sufficiently pronounced 

 to warrant a careful examination of the cranium. 



Dr. Allen has sent to me eight crania for inspection. The characters 

 of these specimens are in many respects quite different from those of 

 31. caUfornicus. The following is the description of this new species: 



Auricle scarcely longer than head; the internal basal lobule rudi- 

 mental and projects about a millimeter beyond the juncture of the 

 interauricular membrane. External basal h)be reduced to a thin ridge 

 which leaves the tragus exposed. Tragus with convex anterior border 

 for basal two-thirds, and an abruptly acuminate apical third. The 

 outer border is straight — apparently without basal notch or lobule. 



The nose-leaf without well-defined lower border — scarcely longer 

 thf n the face. Chin apparently without divided plate. 



SlaiU. — Facial region without depression on the frontal bone; indeed, 

 it is faintly ridged posteriorly ; region over ethmoid scrolls scarcely 

 inflated. Squamosal jwrtion of zygoma not more than one-half the size 

 of the same part in M. californk'us. No jirojection of vertex at occiput, 

 but the entire superior curvature of the head simple. Angle of mandi- 

 ble projects scarcely at all back of the condyloid surface. The two 

 halves of the mandible closer together than in M. caUformcus. 



Teeth. — The lower premolars are more crowded than in M. ealifornicus. 

 The palatal portion of the upper canine is produced to a point posterior 

 to the lateral incisor. 



Fur. — On the back the basal two-third is white, the apical third very 

 dark plumbeous, the tip tending to gray. These distinctions are best 

 defined on the sides of the neck. At the middle of the back the gray 

 tip is absent. The colors undergo no variation over the posterior sur- 

 face of the prebrachium, the humerus, or the rump. On the endo- 

 patagium the hairs are shorter, sparsely developed, and of a fawn color 

 throughout. 



On the venter a disposition exists for the basal two thirds of the hair 

 to be whiter than the rest of the hair. This is most marked on the 

 sides of the trunk, and is nearly absent at tlie middle. The apical 

 third is less markedly plumbeous and the tip is more gray than on the 

 back. On the whole the venter gives the impression of being gray, 

 and the back as being of a dark, sooty hue. 



The posterior surface of the auricle covered with short unicolored 

 gray hair which extends upward along the median b(nder nearly its 

 entire length. The hair extends both on the back and the venter over 

 the fleshy part of the forearm. 



Two immature examples (the distal epiphyses of the metacarpal 

 bones of the third, a fourth, a fifth, manal digits ununited) 2004, 2005 

 (Am. Mus., N. Y.), from Bolanos, Jalisco, Mexico. 



