538 MB. OLDFIELD THOMAS ON [May 15, 



7. Mus PORRESTi Thos. (Plate XXXVII. fig. 1.) 



Abstr. P, Z. S. No, 32, p. 6, May 22, 1906. 



5 . 92, 101, 104, 117, 118, 119. Alexandria. 

 *' Caught on diy grassy plain. Native name ' Keragenga.' 

 Mammas 4."— IF". S, 



Size medium, intermediate between "rat " and "mouse." Fur 

 of medium length ; hairs of back 9-10 mm. long, fairly coarse, but 

 not spinous. General colour above pale " drab-grey," paling to a 

 creamy drab on the sides. Some specimens are, however, more 

 buffy in tone. Under surface pure sharply defined white through- 

 out, the hairs white to their bases. Ears rather short, their 

 proectote pale bi'own, not darker than the general colour of the 

 head ; a tuft of creamy-drab hairs at their anterior base. Upper 

 surface of hands and feet pure white. Tail well-haired, greyish 

 white, little darker along the upper side. 



Skull rather lightly built, with a slender muzzle. Interorbital 

 region narrow, parallel-sided, its centre concave upwards, its 

 edges rounded anteriorly, squared behind, but without ridges. 

 Palatal foramina long, reaching backward to the anterior fourth 

 of m^, unusually narrow, especially posteriorly, their edges 

 rounded. Palate extending in middle line some way behind m^, 

 the interpterygoid fossae commencing further forward than the 

 mesopterygoid one between them ; the former very broad, the 

 latter narrow. Bullse comparatively little swollen. 



Incisors slender, even in old specimens. Molars of rather 

 unusual structure as compared with typical Mus (ratms, &c.), but 

 there is a great deal of variation among the Australian Muridse 

 in this respect, and the characters of M, forresti are led up to by 

 other described species — e. g., M. nanus and M. gouldii. M} with 

 a very strongly marked cingular ledge at its antero-internal 

 corner, practically forming a small supplementary anterior lamina ; 

 the normal anterior and second laminse very strongly slanted 

 backwards intei'nally, their outer cusps hardly perceptible. M' 

 with the large antero-internal cusp (" 6 " of Winge) about equal 

 to the poster 0- external (" 5 "), the normal main lamina between 

 them strongly tilted, as in m\ and with its inner and median 

 cusps subequal, the outer practically absent ; a minute antero- 

 extei-nal supplementary cusp present. Lower teeth unusually 

 brachyodont ; m^ and m^ each with a small median supplementary 

 cusp behind. 



Dimensions of the type : — 



Head and body 104 mm. ; tail 72 ; hind foot 19 ; ear 15. 



Skull — greatest length 25 ; basilar length 21 ; zygomatic 

 breadth 13*5 ; nasals, length 8*5 ; interorbital breadth 3"6 ; 

 palatilar length 13; diastema 7'6 ; palatal foramina 5*5x1 '4; 

 length of upper molar series 4'4. 



Hah. Alexandria. 



Tij2)e. Old female. B.M. No. 6.3.9.39. Original number 118. 

 Collected 10 May, 1905. 



