THE HARVEST MOUSE 



563 



the Harvest Mouse is characterised by the great development of the 

 cerebral, and the corresponding shortening of the facial regions. 

 The smooth, ovate, evenly inflated brain-case nearly equals, and in 

 Far Eastern sub-species occasionally exceeds, the zygomatic breadth in 

 width. The parietal region is well vaulted ; the edges of the short 

 inter-orbital region are quite sharp, though not ridged. The anterior 

 edge of the masseteric plate is straight, not curving forwards, and it 

 scarcely projects beyond the front edge of the slender roof of the 

 infra-orbital canal. The nasals fuse with each other at an early stage 

 of growth; they are short and rather narrow; the processes of the 

 premaxillse supporting them in front are but weakly developed. The 

 diastemata are short, the anterior palatal foramina are relatively about 

 as in A.flavicollis. Notwithstanding the shortness of the rostrum, the 

 palatal length is about as great relatively as in A. sylvaticus ; this 

 is due to the greater development of the posterior palatal shelf, which 

 in this genus has a structure very similar to that oi Microtus {cf. Fig. 89 



Pig. 89. — Skulls of Apodemus and Micromys. 



Apodemus sylvaticus^ (l) dorsal, (2) ventral view ; Micromys minuius, (3) dorsal, 

 (4) ventral view. (1-4 life size.) (5) Palate of Micromys (3 times life size). 



with Fig 73D. above, p. 459). Posterior lateral bridges and fossae, and 

 a posterior median septum, the ventral surface of which is frequently 

 slightly grooved, can all be distinguished just as in Microtus, but 

 these parts, in correlation with the brachyodont teeth, are, of course, 

 sculptured in lower relief in Micromys, and they are situated behind, 

 instead of between, the tooth-rows. The inter-pterygoid space begins 

 about I mm. behind the tooth-rows, and is narrower in front than 

 behind. The basi-occipital is compressed slightly, its anterior width 

 being less than its median length, and the median ridge and lateral 

 furrows of its ventral surface are well defined. The bullae are of 

 large size and rounded form. The following proportional measure- 

 ments (condylo-basal length =ioo), obtained from a series of skulls 

 representing nearly all known sub-species of M. minutus, may be 

 compared instructively with those of Apodemus given in the tables 

 at pp. 519 and 539 above: — (5) Cranial width, 517 to 57-8; (6) cranial 

 depth, 30'9 to 36-6 ; (7) post-molar length, 48 to 50-9 ; (8) condyle to 



