2IO MILLER 



in the region of the anterior zygomatic roots, and in the posterior por- 

 tion of the braincase. The antero-posterior diameter of the inter- 

 parietal is usually greater than in the mainland form ; though this 

 character is not wholly constant it is sufficiently so to differentiate 

 series of specimens. 



Measurements. — External measurements of the type: total length 

 362; head and body 171 ; tail vertebrae 191 ; hind foot 37 (35) ; ear 

 from meatus 20.4; ear from crown 15.8; width of ear 15.6. Average 

 of four adults from the type locality: total length 375 (363-381); 

 head and body 1S4 (171-197); tail vertebrae 189' (184-197) ; hind 

 foot 36.5 (34-38) ; hind foot without claws 34.5 (33-35)' 



Cranial measurements of type: greatest length 43 (41); 'basal 

 length 37 (36) ; basilar length 34 (33.6) ; palatal length 20 (19.4) ; 

 least width of palate between anterior molars 4.4 (4.4) ; diastema 

 1 1.6 (11.4) ; length of incisive foramen 7.8 (7-6) ; combined breadth 

 of incisive foramina 3 (3) ; length of nasals 15.4 (14.4) ; combined 

 breadth of nasals 4.4 (3) ; zygomatic breadth 19 (20) ; interorbital 

 breadth 6 (6.4) ; mastoid breadth 16.4 (16.6) ; breadth of braincase 

 over roots of zygomata 15.4(16.4); depth of braincase at front of 

 basioccipital 11.6 (11); frontopalatal depth at posterior extremity of 

 nasals 9.4 (9.6) ; least depth of rostrum immediately behind incisors 

 7.8 (7.8) ; maxillary toothrow (alveoli) 7 (7.6) ; width of first upper 

 molar 2 (2) ; mandible 33.6 (22.4) ; mandibular toothrow (alveoli) 



7(7)- _ 



Specimens examined. — Elev^en, all from the type locality. 



Remarks. — On comparison of the eleven specimens of Al7is tio- 

 ma}iiciis with ten of the continental race of Mus ' alexandrinns ' 

 from Trong the differences in color are seen to be remarkably con- 

 stant. The slight cranial peculiarities of the insular form, while 

 hardly sufiicient by themselves to separate the animal, are of un- 

 doubted significance when considered in connection with the external 

 characters. For comparison with the allied insular species see de- 

 scription of Mus ta??ibelanicus, p. 213. 



MUS SIANTANICUS sp. nov. 



Type. — Adult male (skin and skull). No. 101705 United States 

 National Museum. From Fulo Siantan, Anambas Islands. Collected 

 September 11, 1S99. 



Characters. — Size, proportions, quality of fur, and color essentially 



' Measurements in parenthesis are those of an adult male Mus ^ alexandri- 

 nus' from Trong (No. 84395). 



