280 Mr. 0. Thomas on 



Oryzoviys videfessus, sp. n. 



Size of 0. galapagoensis, tail much shorter. Skull 

 raarkedlj different. Fur coarse aad sliaggy. General 

 colour above dull raouse-grej, heavily lined witli black ; a 

 slight tinge of fawn in tlie posterior dorsal region. Face 

 slightly paler than back, no darker markings round eyes. 

 Ears of medium size ; a well-marked basal ])rojection on their 

 anterior edge, greyish, the anterior half of their outer surfaces 

 blackish. Under surface greyish white, the hairs everywhere 

 slaty basally, with white tips; line of demarcation on sides 

 not sharply defined. Upper surface of hands and feet white. 

 Tail scarcely longer than the body without the head, well- 

 haired, black above, white below and at the extreme tip. 



Skull, as compared to that of 0. galapagoensis, with a 

 markedly longer and narrower muzzle and with a much 

 narrower interorbital region, the sides of which are evenly 

 concave instead of divergent, so that the least interorbital 

 breadth is at tlie junction of the olfactory and cerebral 

 chambers, instead of considerably in front of that point. 

 Palatal foramina reaching to the first lamina of m}. Palate 

 extending some way behind m}. 



Dimensions of the type (an adult, measured in skin) : — 



Head and body 135 millim.; tail 97; hind foot (wet) 

 s. u. oO, c. u. 31'5; ear (dry) 18. 



Skull : greatest length 35*3 ; basilar length from hen- 

 selion 26*5; greatest breadth 18; nasals 14*5 x 3*6; inter- 

 orbital breadth 43; interparietal 2'9xl0; palate length 

 from henselion 15; diastema 9; palatal foramina 6*5x24; 

 length of upper molar series 5*3. 



Hah. Indefatigable Island, Galapagos. 



Tgpe B.M. no. 99. 8. 28. 1. Collected Aug. 31, 1897, by 

 Messrs. Webster and Harris. Two specimens examined. 



This is the third Oryzomys described from the Galapagos 

 Archipelago, the first being the original ^'' Mas galapagotnsis^^ 

 of Waterhouse *, from which it differs as above mentioned, 

 and the second being 0. Bauri, Allen t, a species with an 

 even longer tail than 0. galapagoensis. A bat of the genus 

 AtalopJia is the only other indigenous mammalian inhabitant 

 of the islands. 



Iieithrodon fossor, sp. n. 



Precisely similar in external appearance to Akodon ma- 

 cronyx. Fur soft, about 10 millim. long on the back. 



* Zool. Voy. 'Beagle,' Manini. p. Qo (1839). 

 t Bull. Am. Mus. iv. p. 48 (1892). 



