INTERRELATIONSHIPS OF GENERA 85 



bordering the alveolar sheath of the lower incisor as it ascends the 

 condylar process. 



The incisor teeth are highly specialized; they are much 

 lengthened and straightened, forming smaller segments of much 

 larger circles than usual ; they are without grooves, and, as is very 

 commonly the case in Rodent incisors showing fossorial adapta- 



Ellohius lancrci Blasius. 



Right mandibular ramus dissected to show the alveolar courses of the 

 teeth. The small figure represents the left mandibular ramus in oblique 

 posterior view and shows the relation of the alveolar protuberance of 

 the incisor to the condyle (enlarged). 



tion, their enamel is white and they tend to be rounded in 

 transverse section. The upper incisors extend much further back- 

 wards in the maxillary bones than in any other Microtine genus, 

 their alveolar capsules terminating just dorsal to the surface of the 

 palate between the molars at a point near the hinder end of m^ ; 

 in some species the ends of the capsules actually appear on the 

 surface of the palate, a fenestra by absorption of bone being 

 opened in the maxilla before the advance of the growing tooth. 

 The lower incisors are also very long, ascending the condylar 



