MAMMALS FROM MOUNT COFFEE, LIBERIA 643 



middle of proencephalon. Ratio of depth of rostrum at posterior ex- 

 tremity of nasals to basilar length 36.8 in A. njiivittctiiis^ 28 in A. 

 ' planifrons. Antorbital foramen narrower than in A. tmivittat/is, the 

 difference similar to that between JMus defua and Af. rutilans^ though 

 less. Plate of maxillary forming outer wall of antorbital foramen 

 narrow, its anterior margin sloping gradually upward and backward, 

 its width at middle 3 mm. In A. univittatus the anterior margin 

 rises vertically to slightly above middle and then bends abruptly back- 

 ward, forming a conspicuous angle. The width at middle is about 4 

 mm. Incisive foramina shorter and wider than in A. utiivittatiis^ 

 the median septum very widely expa?ided at level above (dorsal to) 

 palatal surface. Audital bullae larger than in A. utiivittatus^ but not 

 essentially different in form. Mandible much more slender than that 

 of A. tmivittatus^ especially the posterior portion. 



Teeth. — The teeth are broader than those of A. univittattis^ but I 

 can detect no difference in the enamel folds. 



Measurements. — External measurements of type^ : total length 331 ; 

 tail vertebrae 98; hind foot 30 (37.6) ; ear from meatus 14.8 ; ear from 

 crown 10; width of ear 13.8. 



Cranial measurements of type: greatest length 34 (33.6)^; basal 

 length 38(27.6); palatal length 14(14.4); palatal width between 

 anterior molars 3.8 (4.3); diastema %.(> (8.4); length of incisive 

 foramen 5.6 (6.4) ; combined width of incisive foramina 3.8 (2.4) ; 

 length of nasals 13.6 (13); combined breadth of nasals 4.2 (4); 

 zygomatic breadth 15 (16.6); mastoid breadth 11 (13); interorbital 

 breadth 6.4 (6.4) ; breadth of braincase above roots of zygomata 14 

 (15); depth of braincase at front of basioccipital 10(9.6); fronto- 

 palatal depth at posterior extremity of nasals 7 (9-2) ; least depth of 

 rostrum behind incisors 5.4 (6) ; maxillary toothrow (alveoli) 5.8 

 (5.8) ; breadth of first upper molar 2 (3.4) ; mandible 17.6 (18.4) ; 

 mandibular toothrow (alveoli) 5.4 (6). 



Sf)ecime7is exattiined. — Two, both from the type locality; one not 

 fully adult. 



Remarks. — The external similarity of this animal to Arvicanthis 

 univittatus forms a striking contrast to the distinctness of its cranial 

 characters. These are as marked in the immature individual as in the 

 adult. 



1 Three specimens of A. univittatus from Benito River, Cameroon, average : 

 total length 242 ; total vertebrte 105 ; hind foot 30 (28). 



^Measurements in parenthesis are those of a somewhat older individual of 

 A. univittatus from Benito River. 



