On new South- American Rodents. 503 



Dimensions of the type (measured in flesh) : — 



Head and body 92 mm. ; tail 125; hind foot 16; ear 19. 



Skull : greatest length 27*2 ; basal length 24*4 ; greatest 

 breadth 15; nasals llx2"8; interorbital breadth 46; 

 breadth of brain-case 11*2; palatal length 14 '3; combined 

 length of three molariform teetli 4'4 ; breadth across outer 

 corners of m 3 8*5. 



Type. Adult female. Original number 64. Collected 

 15th June, 1910. 



This pretty little species has a considerable external 

 resemblance to the M. marica of Merida, Venezuela, but is 

 probably really most nearly allied to M. microtarsus, from 

 which it differs by its paler colour and rudimentary post- 

 orbital processes. The variation in the coloration of the 

 belly-hairs is unusual in this group. 



"Catita pequefia." — E. S. 



LVII. — Four new South- American Rodents, 

 By Oldfield Thomas. 



(Published by permission of the Trustees of the British Museum.) 



Sciurus {Microsciurus) similis fusculus, subsp. n. 



A lowland race of S. siinilis*. 



All characters as in similis, except that the olivaceous tone 

 of the upper surface is replaced by blackish brown (darker 

 than " vandyke-brown "), the fine rings on the hairs, buffy in 

 similis, reduced in prominence and tending towards tawny. 

 On the face and sides this alteration from buffy to tawny or 

 tawny ochraceous is particularly evident. Colour of chest 

 also rather "tawny ochraceous" than "ochraceous," as it is 

 in similis. 



Dimensions of the type (measured in the flesh) : — 



Head and body 126 mm. ; tail 108 ; hind foot (s. u.) 33 ; 

 ear 13*5. 



Hah. Choc<5, W. Colombia. Type from Juntas, Rio San 

 Juan. Alt. 400'. 



Type. Adult male. B.M. no. 10. 7. 16. 2. Original 

 number 141. Collected 27th February, 1909, by Mervyn G. 

 Palmer. Two specimens. 



* Nelson, Bull. Am. Mus. N. II. xii. p. 78 (1899). 



