ALLEN: mammalia: octodontid^. 43 



Ctenomys colburni Allen. 



(Plate VIII, Figs. 3 and 4, Skull.) 



Ctetiomys colburni Allen, Bull. Am. Mus. Nat. Hist., XIX, 188, May 9, 

 1903. Arroyo Aike, in the Basalt Canons, fifty miles southeast of 

 Lake Buenos Aires, Patagonia. 



Similar to C. sericeus but larger, much more strongly suffused with 

 fulvous and less varied with black. 



Measitremeufs. — Type: Total length, 230 mm. ; tail vertebrae, 65; hind 

 foot, 29. Fifteen males measure as follows: Total length 224.5 (210- 

 240, with one at 245 and one at 250) ; tail vertebrae, 69 (60-75, with 

 two at 80); hind foot, 30 (28-32, and one at 33). Seventeen females: 

 Total length, 213 (200-225); tail vertebrae, 62.2 (60-65); hind foot, 29.5 



(29-31)- 



Skitll. — Type, total length, 43 ; basal length, 39 ; zygomatic breadth, 



25 ; mastoid breadth, 25 ; interorbital breadth, 8.5 ; length of nasals, 



14.3; palatal length, 20; diastema, 6; upper molar teeth, 8; lower jaw, 



inner base of incisors to posterior border of condyles, 28.5 ; inner base of 



incisors to point of angular process, 33.5 ; height at condyle, 8 ; width 



between condyles, 16; width between points of angular processes, 27; 



lower molar teeth, 8.5. Seven old male skulls measure : Total length, 



43 (41-45) ; zygomatic breadth, 24.3 (23.5-25.3) Fifteen old female 



skulls: Total length, 38 (36-41); zygomatic breadth, 22.2 (21-24). 



Represented by 33 specimens — 16 males and 17 females — all adult 

 except 3, and all collected by Mr. Colburn, of which 16 were taken in the 

 basalt canons, fifty miles southeast of Lake Buenos Aires, April 2 to 26, 

 and the remaining 17 at Swan Lake, April 2 to May 17. 



Aside from the young specimens, which are grayer and much less ful- 

 vous than the adults, the variation in color consists in some specimens 

 being a little more strongly suffused with yellowish than others, and in 

 the distinctness of the tail stripe, which is often wholly wanting, or pres- 

 ent in varying degrees from a faint trace to a broad black stripe. 



This species is intermediate in size between C. sericeus and C. mendo- 

 cina, being larger than the former, and differing from it in its more strongly 

 fulvous and generally lighter coloration, and from the latter in consider- 

 ably smaller size and entire absence of any reddish suffusion. 



It is of interest to note that this species was not obtained by Mr. Peterson 



