the River Supinaam, Demerara. 187 



its allies by its rich rufous colour. It is probably a Guianan 

 representative of the Brazilian 0. intermedins, Leche, but is 

 more brightly coloured. 



I have named it in honour of the donor of the collection, 

 Mr. F. V. McConnell, to whom the National Museum owes 

 not only this but many other valuable donations. 



Four. 



0. laticeps group. 



11. Oryzomys sp. 



12. CEcomys guiance, sp. n. 



Eight. 



A Targe species, the hairs of the belly grey-based. 



General characters Yery much as in CE. marmosurus. Size 

 rather less than in that species, the feet noticeably shorter. 

 Colour above between " tawny " and " clay-colour/' distinctly 

 darker and more brownish than in CE. marmosurus. Under 

 surface dull buffy whitish, the bases of the hairs, except just 

 on the chin and throat, slaty grey, even down the centre line 

 of the belly ; laterally the line of demarcation is sharper than 

 in marmoswus, less sharp than in tapajinus ; a dull buffy line 

 along the lower edge of the colour of the flanks. Hands and 

 feet pale brown, the fine hairs with a silvery gloss. Tail 

 uniform dark brown above and below, the hairy part at its 

 base less than in CE. marmosurus. 



Skull and teeth as in CE. marmosurus. 



Dimensions of the type (measured in skin) : — 



Head and body 115 mm.; tail 155; hind foot 26; ear 16. 



Skull: greatest length 32*7; zygomatic breadth 17'?; 

 palatal foramina 5*7 ; upper molar series 4*9. 



Type. Adult female. B.M. no. 10. 5. 4. 23. 



The three large species of CEcomys from N.E. South 

 America, CE. marmosurus, tapajinus, and the present one, are 

 all very similar in size and cranial characters, but are distin- 

 guishable by the colour of the under surface. In CE. marmo- 

 surus this passes quite gradually into the colour of the sides, 

 without line of demarcation, and the hairs of the middle line 

 of chest and belly are white to their bases. In CE. tapajinus 

 all the hairs below are completely white, except just along the 

 sides of the belly, and there is a very sharply defined lateral 

 line of demarcation. In CE. guiance all the hairs below are 

 slate-based and the lateral line is of an intermediate degree 

 of definition. 



