netc African Mammals. 227 



tliosc on the other toes. E;ir.^ rounded and simple, with no 

 internal foUis such as occur in Dendromus. Tail long and 

 alm(^-!t naked. 



8kull with a broad square-shaped brain-case ; zygomatic 

 breadth very nuicli greater than in Deri'lromus, zygoma set 

 in a nearly parallel position. (Squamosal jiortion of zygoma 

 bro.id and horizontally expanded. Palate and pter^-goid 

 regions much as in Dendromus. Palatal foramina and 

 nasals much shorter than in Dendromus. Lower jaw with 

 very short coronoid processes, not rising above t!ie level of 

 the condyles. Angular processes inflected inwards, more so 

 than in Dendromus. 



Teeth : upper incisors short, slender, ungrooved, and 

 thrown forwards, projecting anteriorly beyond the nasals, 

 somewhat as in Uranomys. Upper molar teeth broad and 

 fairly largo, highly cuspidate; the cusps arranged very much 

 as in Dendromus J though in Prionomi/s the cusps are raised 

 up into sharp recurved points, their grinding-surfaces facing 

 backwards, resembling in this respect the genus Alylomys. 

 Cusp-formula of the three laminpe of m} as in ordinary 

 Dendromyina?, 2.3.2. Internal cu^p large and well-deve- 

 loped. Longitudinal grooves between the outer and median 

 cusps and median and inner cusps, sharjdy defined, the outer 

 of the two grooves straight and uninterrupted throughout the 

 whole lenfjtli of the tooth. Outer cusps of the three laminre 

 rather taller than those of the median series and laterally 

 compressed. No trace of the small median anterior suppK'- 

 mentary cusp which is present in Dendromus. M^ with cusj)s 

 arranged on much the same plan as in w\ the two longitu- 

 dinal grooves well-marked and the cusps avicularian. Inner 

 cusp well developed. Longitudinal groove between median 

 and external cusps of the lamina3 as evident as in m\ M^ 

 small and simple, composed, as in Dendromus, of two small 

 cusps with a groove between them. Lower incisors slender 

 and sharply })ointed, set in a more horizontal position than in 

 Dendromus. Lower molars, like the upper series, highly 

 cuspidate, only here the cusps are curved in the opposite 

 direction, their tips and concave grinding-surfaces facing 

 forwards. 3/, composed of three laminae of two cusps each, 

 cusp-formula 2.2.2. Median longitudinal groove between 

 the outer and inner cusps of the three laminaj deep, straight, 

 and clearly defined. Postero-internal cusp small. Inner 

 cusps, wiih the exception of the postero-internal, rather taller 

 than outer series. J/j with four prominent cusps, two on 

 either side of the deep longitudinal groove, i/, larger than 



lb* 



