Miller. Seven New Rats collected in Siam. 139 



ly, and uniformly annulated. At middle there are only seven or eight 

 rings to the centimeter. The rings are irregularly and inconspicuously 

 marked by cross furrows dividing them into sharply rectangular scales 

 longer than broad. Numerous stiff hairs spring from beneath the free 

 edges of the rings, usually three to each scale. In length they scarcely 

 exceed width of the rings, except near tip where they become longer 

 and less stiff. 



8kuU. The skull of Mus vodferans (Pis. Ill and IV, Fig. 3) is large, but 

 in proportion to its size not very heavily built. In general appearance 

 it differs only slightly from that of M. sabanus. On comparison it is 

 seen to differ from that of the Bornean species in less robust rostrum, 

 less elevated frontal region between roots of zygomata, and in the form 

 of the antorbital foramen. This is smaller and more contracted, espec 

 ially below, and the maxillary plate forming the outer wall is wider and 

 less concave. The front edge of this plate is nearly straight, though 

 slightly convex above. The audital bullse like those, of Mus sabanus are 

 relatively very small, scarcely more than half as large as in Mus decum- 

 anus. By this character alone the species may be distinguished from 

 the other large rats of the Malay Peninsula. 



Teeth. The teeth appear to agree in all respects with those of Mus 

 sabanus, though I have seen none of the latter unworn. The enamel 

 pattern is like that of M. decumanus except that there is no trace of ru 

 dimentary anterior outer tubercle often present in the second upper 

 molar of the houserat. As in this species the posterior upper 

 molar consists of an anterior inner tubercle followed by a crescentic loop 

 with concavity directed inward. In unworn teeth this loop is normally 

 complete, though in some specimens the posterior limb is divided by a 

 furrow. With abrasion the limbs of the crescent become separated. 

 Front surface of incisors deep orange. 



Measurements. External measurements of type: total length, 611; 

 head and body, 229; tail vertebrae, 382; hind foot, 45 (43)*; ear from 

 meatus, 24; ear from crown, 19; width of ear, 18. Seven specimens 

 (including type): total length, 566 (545-611); head and body, 224 (216- 

 229); tail vertebrae, 342 (323-380); hind foot, 45 (42-48>; hind foot without 

 claw, 43 (40-46). 



Cranial measurements of type: greatest length, 56; basal length, 

 47.6; basilar length, 44.6; palatal length, 25; least width of palate be 

 tween anterior molars, 5; diastema, 14.8; length of incisive foramen, 8; 

 combined breadth of incisive foramina, 3.8; length of nasals, 21.4; com 

 bined breadth of nasals, 6.2; zygomatic breadth, 25.8; interorbital 

 breadth, 9; breadth of braincase above roots of zygomata, 20.4; mastoid 

 breadth, 18.8; occipital depth at front of basioccipital, 14; frontopalatal 

 depth at posterior extremity of nasals, 13.6; least depth of rostrum im 

 mediately behind incisors, 11; maxillary toothrow (alveoli), 11.8; width 

 of front upper molar, 3; mandible, 30.6; mandibular toothrow (alveoli), 

 10. 



^Measurement of hind foot in parenthesis is taken exclusive of claws. 



