MICROTUS 661 



First lower molar with four or five re-entrant 

 angles on outer side. 

 Nasals moderately cuneate, their combined 

 breadth posteriorly a little more than half 

 their greatest breadth ; diastema notice- 

 ably shorter than nasals. 

 Condylobasal length of skull about 27 mm. ; 

 upper tooth-row about 7 mm. , the teeth 



not unusually robust (Central Spain) M. cabrern', p. 701. 



Condylobasal length of skull about 30 mm. ; 

 upper tooth-row about 8 mm., the teeth 



unusually robust (South-eastern Spain) M. clentatus, p. 703. 

 Nasals strongly cuneate, their combined breadth 

 posteriorly much less than half that ante- 

 riorly ; diastema usually longer than nasal, 

 never noticeably shorter. 

 Largest skulls with condylobasal length 

 about 27 to 30 mm. 

 Kostrum very short and deep (distance 

 from front of zygoma to tip of nasal 

 less than depth of rostrum through 

 posterior extremity of nasal) ; nasal 

 forming very conspicuous angle (about 

 34"^) with dorsal surface of interorbital 



region (Southern Hungary) M. angiUaris, p. 706. 



Rostrum normal in form (distance from 

 front of zygoma to tip of nasal greater 

 than depth of rostrum through pos- 

 terior extremity of nasal) ; nasal not 

 forming very conspicuous angle (about 

 20°) with dorsal surface of interorbital 

 region. 

 Auditory bullae unusually large ; upper 

 molars with osteodentine spaces re- 

 duced (Thessaly) M. hartituji, p. 704. 



Auditory bullae not unusually large; 

 upper molars with osteodentine 

 spaces of normal width. 

 General form of skull narrow and 

 agrestis-like ; median ridge of pos- 

 terior termination of bony palate 

 without evident groove along su- 

 ture ; zygomata not conspicuously 

 expanded at middle ; underparts 

 pale clear grey (Channel Islands). M. sarnius, p. 700. 

 General form of skull broad, not 

 agrestis-\\kti ; median ridge of pos- 

 terior termination of bony palate 

 with evident groove along suture ; 

 zygomata conspicuously expanded 

 at middle in adults ; underparts 

 brownish buff or buffy grey (Ork- 

 ney Islands). 

 Brain-case not flattened, the ratio 

 of occipital depth to width 

 about 57 ; condylobasal length 

 of largest skulls 28 to 29 '6 mm. 



(South Orkney Islands) M. orcadensis, p. 694. 



Brain-case flattened, the ratio of 

 occipital depth to width about 

 58 ; condylobasal length of 



