398 MICROTIN^ 



rather long hairs (4-5 mm.) which do not completely conceal the 

 annulations ; the hair (particularly in old specimens) longer and 

 denser upon its imder than upon its upper surface. Flank glands 

 are present in both sexes, oval in shape (measuring 17 X 12 mm.), 

 and each with its long axis parallel to that of the body; surface 

 of gland slightly raised, closely and irregularly wrinkled and 

 pitted so as to produce a honeycombed appearance; from the 

 cavities of the pits hairs, resembling those of the ordinary 

 pelage, arise ; these hairs become scarcer towards the centre of 

 the gland. Mammae, 2 — 2 = 8. 



Fur close, dense and long ; the under fur thick and woolly. 

 Colour of upper parts normally dark brown, ranging from " broccoli 

 brown " to " mars brown " or darker, darkest along the spine, 

 palest on the face and sides, but without noticeable contrasts ; 

 sides usually lined with black, the cheeks and ears usually tinged 

 with ochraceous bufi or light raw umber. Under surface varying 

 between ochraceous-bufi and slate grey, the latter tint produced 

 by the dark bases of the hairs. Feet ranging from " hair brown " 

 to "ecru drab," sometimes blackish. Tail blackish; its under 

 surface sprinkled with greyish hairs. 



Two irregular moults (spring and autumn) occur ; the summer 

 coat is shorter and often redder, owing to the absence or scarcity 

 of long hairs with dark tips. In the young the juvenal coat is 

 black ; the post-juvenal coat resembles the summer adult pelage. 



Skull (Figs. 1-8, 107) large and massive, strongly ridged and 

 angular when fully adult, but not essentially different from that 

 of Microtus. Rostrum long and stout, distinctly broader than 

 interorbital region in adults. Zygomatic arches strong, widely 

 spreading, their greatest width behind over squamosal roots. 

 Upper incisors moderately protruding, their front faces entirely 

 visible in the dorsal view beyond the tips of the nasals. Nasals 

 short and rather narrow, their greatest width always noticeably 

 less than the width of the rostrum. Interorbital region short, but 

 much constricted posteriorly. Braincase distinctly longer than 

 broad, its outline in dorsal view nearly rectangular. Temporal 

 ridges strongly developed in adults; fusing in the interorbital 

 region to form a sharp, and eventually a lofty, median crest ; well 

 marked on the surface of the braincase, diverging from the 

 interorbital crest and running back for the most part along the 

 upper edges of the squamosals to points above the glenoid 

 articulations and thence converging again, traversing the lateral 

 wings of the parietals and the extremities of the interparietal, 

 to the lambdoid crest. In youth the ridges and the squamosals 

 are widely separated ; but with growth they approach each other, 

 the squamosals creeping upwards and inwards over the frontals 

 and parietals (Figs. 1 and 2). Post-orbital squamosal crests 

 long and salient in adult skulls, giving the fore-part of the 

 braincase its rectangular appearance. Occiput nearly verti- 

 cally truncated in younger stages of growth, becoming more 



