ON MAMMALS FROM NEW GUINEA. 727 



with the variation in size usual in the genus, some difficulty lias been found in determining 

 every spécimen. 



15. f Rattus mordax tramitius, Thos. 



cf. 103. 116, 120, 142, 162. Q. 60, 71, 86, 115, 133, 150. 157, 167, 170, Doormanpad-bivak. 

 W. C. van Heurn. 



General characters about as in true mordax, but the colour without the strong rufous 

 or fulvous suffusion that generally occurs in mordax on both upper and lower surfaces. The 

 back blackish grey, very finely ticked with buffy, the ticking and grizzling distinctly finer 

 than in mordax. Undersurface pale slaty grey, washed with clay colour, a white patch often 

 présent on the chest. 



Skull as in mordax. 



Dimensions of the type, measured in flesh : 



Head and body 175 mm.; tail 170 ; hindfoot 35.5. 



Skull, greatest length 41.5; condylo-incisive length 38; zygomatic breadth 20; inter- 

 orbital breadth 6.2 ; palatal foramina 7.4 ; upper molar séries 7. 



Hab. as above ; Type from Doormanpad-bivak. 



Type. Adult female. B. M. N°. 22. 2. 2. 13, Original number 86. Collected 15 October 

 1920 by W. C. van Heurn. 



The spécimens collected on the south side of the Nassau range by the British Expé- 

 ditions appear also to belong to this less rufous form. 



16. f Rattus coenorum, Thos. 



cf. 26, 27, Q. 19, 20, 23, 24, Pionier-bivak, Mam'beramo River, W. C. van Heurn. 

 cf. 44, 48, 224. 225. Q. 46. 47. Prauwen-bivak, Idenburg River, W. C. van Heurn. 

 Q. 197. Doorman-rivier. W. C. van Heurn. 



A thickly built, heavy-footed form related to R. mordax, but larger. Fur largely con- 

 sisting of slender spines. General colour dark fuscous, the spines with grey bases and black 

 ends, the hairs between them with glistening buffy tips, unusually bright and glossy; but in 

 old spécimens the fur becomes a draggled muddy colour. Under surface dull whitish, the 

 spinous hairs wholly whitish, the ordinary hairs pale slaty. Fingers whitish, metacarpals more 

 or less brown. Hind feet greyish white, the terminal part of the metatarsus commonly brown. 

 Tail coarsely scaled, almost naked, blackish brown. 



Skull essentially similar to that of mordax, but larger and more robust. Mammae 2 — 2 = 8. 



Dimensions of the type, measured in flesh: 



Head and body 207 mm.; tail 230 ; hindfoot 44. 



Skull of type and of a very old maie, inserted for comparison with that of the next 

 species, greatest length 47, 47.6; condylo-incisive length 44.3, 46; zygomatic breadth 22.7, 

 24.4; nasals 16.6, 19.4; interorbital breadth 6.5, 6.5; breadth between ridges on brain-case 

 15.7, 15; zygomatic plate 5, 5; palatilar length 22, 2; palatal foramina 8. S, 8; upper molar 

 séries 8.3, 7.8. 



Hab. as above. Type from Pionier-bivak, Mamberamo River. 



Type. Adult maie. B.M. N°. 22. 2. 2. 19. Original number 26. Collected 18 Dec. 1920. 



