Mr. O. Thoinu.s on a new Species o/*Perognathus. 40") 



Skull unusually broad considering its small size. Nasals 

 very broad behind, surpassing in length the preniaxillary 

 processes. Interorbital space very broad. Supraorbital beads 

 widely divergent. Anterior and posterior edges of inter- 

 parietal tbrniing two nearly equal curves. Anterior palatine 

 foramina ending in front of ?*-J a distance nearly equal to the 

 length of !!lli^ Posterior nares widely open, rounded. 



Teeth small and delicate. 



Dimensions of the type (B.M. 93. 3. 6. 25), an old male in 

 skin : — 



Head and body 97 millim. ; tail 127; hind foot, without 

 claws (damped) 27, witii claws 28 ; ear from notch 18. 



Skull (see below). 



Hob. Mineral San Sebastian, Jalisco, Mexico. Coll. 

 Dr. A. C. Buller, Jan. 25, 1893. 



The ^y\>Q specimen of this species being quite old, with the 

 molar teeth much worn down, its small size will readily 

 distinguish it from all its allies, except the still smaller 

 0. Alfan\ Allen, from Costa ilica. 



Measurements of the Skulls of the above Species. 



Oryzomys C'ouesi. 



-\ ^ 



Hacienda O.fulyens. O.melaiiotis. 



'lyp*^)?- Cubilguitz, cJ . Tvpe,c?. Type.d". 



millim. millim. millim. millim. 



Basal length (c.) 2G-6 30 4 2o-l 



Upper length* (c.) 305 34-8 (31-8 1) 29-5 



Zygomatic breadth 17'8 (c.) 17-8 (c.) lo-2 



Nasals, length IM 14-1 13-2 120 



Interorbital breadth . . (c.) 5-2 5-9 4-8 5-1 



Breadth of brain-case . 127 13-2 12-8 



Interparietal, length . . 3-5 3*3 3-4 



breadth.. 7-9 7-8 .... 100 



Palate-length 17-7 .... 15o 



Diastema.. 8-G 9-3 9-1 8] 



Length of palatine fo- 

 ramina 6'2 7"0 7"2 58 



Length of upper molar 



series 48 4-8 5-2 4*3 



LXVI. — Description of a new Species of VtxogwutXnx?, from 

 Colorado. By Oldfield Thomas. 



Among a series of what appear, from Dr. Merriam's able 

 monograph, to be Perognathus favus, Bd., collected by 

 Mr. \V. G. Smith in Colorado and acquired by the British 

 Museum, there is a single specimen obviously diflferent from 



* To back of interparietal, excluding supraoccipital. 

 + Interparietal lost ; from back of parietal suture only. 



Ann. cC- ^foq. X. Hist. Ser. G. Vol xi. 29 " 



