new Forms of A.kodou arid Phyllotis. 407 



Phyllotis melaninsj sp. n. 



A VhyUotis with the proportions and bhickish colour of 

 Oryzomi/s calirjinosus and Akodon ccrosus. 



Size about as in Akodon cerosus. Fur fine, ratlier crisp, 

 liairs of back al)out 6'0— 6"5 mm. in length. General colour 

 dark sepia or bistro, slightly greyer and less warm than in 

 the two species above mentioned ; median dorsal area rather 

 blacker than the rest. Punctulation of the fur fine, about as 

 in the Akodon, not so distinctly lined as in the Oryzomya. 

 Under surface soiled buffy greyish, more different from the 

 upper surface than in the species in question. Ears short, as 

 in the similar species, not as in ordinary Phyllotis; greyish 

 brown, the proectote blackish. Hands and feet greyish 

 brown, a patch in the middle of each metapodial blackish 

 brown. Tail shorter than head and body, markedly more 

 hairy than in the Oryzomys or Akodon, brown above, dull 

 greyish white below. 



Skull similar in shape to that of Phyllotis andium, but 

 rather larger. Supraorbital edges sharply square. Teeth 

 proportionally small. 



Dimensions of the type (measured in flesh) : — 

 Head and body 105 mm. ; tail 78; hind foot 22 ; ear 16. 

 Skull : greatest length 28'5 ; condylo-iiicisive length 25 ; 

 zygomatic breadth 15; nasals 10"8 ; interorbital breadth 4; 

 breadth of brain-case 13*1 ; palatilar length 13 ; palatal 

 foramina 7 ; upper molar series 4'3. 



}Iah. Porvenir, Bolivar, Ecuador. Alt. 1800 m. 

 Type. Adult, male. B.M. no. 99. 9. 9. 107. Original 

 number 258. Collected 12th March, 1899, by P.O.Simons. 

 Presented by Oldfield Thomas. 



This animal carries on one of the most remarkable cases 

 of geographical isomorphism known to me. The practical 

 identity in external appearance of Oryzomys (Melanomys) 

 caliginosus and Akodon cerosus was already known (thouorh, 

 as shown above, under erroneous names). And now, mixed 

 up with Mr. Simons's Akodons, I find a third similar blackish 

 species a member of the genus Phyllotis^ as shown by its 

 skull and teeth. By its slightly lighter underside, its more 

 hairy and faintly bicolor tail, and its not wholly dark feet it 

 is just distinguishable externally from the other two ; but the 

 resemblance is still so great as to excuse anyone for confusing 

 it with them. The three, therefore — Oryzomys^ Akodon, and 

 Phyllotis, — all inhabiting the same region, are so similar to 



