Suhyeyiera of the Sciuropterus Group. 5 



needs further division into subgenera, of which tliere appear 

 to me to be at least four. These may be distinguished as 

 follows : — 



A. Bullae well inflated. Molar ridges high. 

 a. MammjB 8. (Ilolarctic.) 



a"*. Posterior transverse ridge of ^*, ?n', and m^ deeply 

 notched, so as to cut off a separate cusp in the 

 centre of the tooth Sciuropterus. 



J'. Transverse ridges of teeth complete, as usual. . . . Glaucomys. 

 h. ]\Iamma3 G. (Oriental.) 



c\ Bullae well inflated, often double. Molar ridges 



complete Hylopelcs. 



B. Bullae low, flat, little inflated. Molars with lower 



ridges, their enamel usually much sculptured, and 

 with supplementary cusps between the transverse 

 ridges externally Pctinotnys. 



Subgenus Sciuropterus. 



Teeth more complex than in otiier members of the genus, 

 the cusps and ridges high and well defined. Internal wall of 

 each tooth grooved on its lingual aspect, so as to be move or 

 less divided into three, and approaching Belomys in this 

 respect. Posterior transverse ridge of jA, m^, and m^ deeply 

 notched halfway across at right angles to its length, its 

 dividing-line from the inner wall of the tooth also more 

 deeply notched in ; as a result a distinct conical cusp is 

 isolated in the centre of the tooth. No similar structure is 

 found in any other member of the group. 



Skull : muzzle narrow, witli parallel sides which are nearly 

 at right angles to the spring of the zygomatic arch. Palatal 

 foramina comparatively large. 



llange. Palffiarctic liegion from Scandinavia to Japan. 



Type — Sciuroptei'us russicus, Tiedem. 



Other species : 6'. momonga, Temra. ; S. hiichnerij Sat. ; 

 S. aluco, Thos. 



Glaucomys, subgen. nov. 



Teeth comparatively simide ; a slight tendency to the 

 develoj)ment of grooves on the lingual side of the internal 

 wall. Posterior transverse ridges complete, partially joined 

 internally to the outer slope of the internal wall, and without 

 any notch halfway across the tooth. 



J\luzzle long, tapered forwards, its sides meeting the spring 

 of the zygomata at u slant. Palatal foramina comparatively 

 small. 



Mamnui: 8. 



