1896.] NATURAL SCIENCES OF PHILADELPHIA. 531 



No. 3,851 9 , - • • November 7, 1894. 



No. 3,883 Juv. 9 , 



No. 3,892 Juv. 9 November 1, 1894. 



No. 3,893 Juv. 9 , November 1, 1894. 



No. 3,906 i , 



No. 3,908 9 , 



Pseudoconomys Subgen. nov. Type J/(/»p)-oco)ioo?o)! (infra). 



Sul)generic characters. Alveolar length of anterior upper molar 

 nearly thrice the greatest width of tooth. The two posterior sets of 

 transverse tubercles of this tooth as in the genus J/«.s, but the ante- 

 rior base of the median anterior cusp is remarkably produced for- 

 ward one-third the whole length of the tooth, and terminates ante- 

 riorly just above the descending tooth root in a false, rounded tuber- 

 cular cone, which lies so far below the grinding plane of the molars 

 as never (?) to become functional. 



36. Mus (Pseudoconomys) proconodon sp. nov. False-cusp Mouse. 



Type, No. 3,880, ad. 9 ; collection of the Academy of Natural 

 Sciences of Philadelphia. Collected by Dr. A.Donaldson Smitli at 

 Sheikh Husein, Western Somaliland, Africa, October 13, 1894. 



Description — Size small, tail minutely and sparsely haired, as 

 long as body \\jithout head, unicolor, very slender and finely annula- 

 ted. Pelage fine, silky, tricolor, mouse brown above, ochraceous- 

 fawn along sides, beneath white. Anterior soles of feet thickly set 

 with granulated points, the hind foot with two anterior, two median 

 and two posterior tubercles, the fore foot with three anterior and two 

 posterior tubercles. Ears very small and rounded. 



Color above, including head and tail, almost exactly as in Mus 

 musculus, the sides slightly tinged with fawn. A well defined red- 

 dish-fawn stripe along sides, from shoulder to hip-joint, distinctly 

 separates the color of back from the pure white of belly. Whole of 

 under side, including upper lips, pure clear white to the bases of the 

 hairs. Feet whitish-brown ; soles naked to heel. Mammae, 2 pec- 

 toral, 2 axillary, 2 abdominal, 2 inguinal. Skull characters as 

 above defined for the subgenus. 



Measurements — Total length, 128 mm. ; tail vertebrae, 56 ; hind 

 foot, 16 ; ear, from crown, 6. 



Skull— Total length, 22; basilar length, 19; greatest width, 11 ; 

 interorbital constriction, 4 ; nasal length, 8.8 ; alveolar length of 

 upper molar series, 4.2 ; length of mandible, 13; greatest width of 

 mandible, 6.4. 



35 



