~ 
Two new Argentine Rodents. 305 
interorbital breadth 9, 8°33; least breadth across brain-case 
18°5, 18; greatest breadth on bullee 26°8, 25°3 ; bulle, length 
diagonally in horizontal plane 18,17 ; breadth at right angles 
to last 9°5, 9. Upper molar series (alveoli) 10:9. 
Hab. Bonifacio, S.W. Buenos Ayres Province, about 
36° 40’ S., 62° W. Other specimens from Papin, El Inca 
(thanks to the help of Mr. George Hughes), and La Zauja in 
the same region. Alt. 50 m. 
Type. Adult male. Original number 2639. Collected by 
R. Kemp, 27th May, 1916. Sixteen specimens. 
Just as Ct. azare, which occurs in the western half of the 
Buenos Ayres Pampas, from General Acha to San Rafael, 
differs from the Eastern Ct. talarum (La Plata to Bahia 
Blanca) by its slightly larger size and much larger bull, so 
it ig in turn exceeded in both respects by the present form, 
which occurs between the two. The blackened area on the 
back also distinguishes this species, no such darkened area 
being present in azare. 
J have named this distinct Tuco-tuco in honour of Don Cecil 
Porteous, but in doing so I may also recall the help 
Mr. Kemp has received from Col. J. J. Porteous in various 
matters connected with his trip. 
The fine series obtained by Mr. Kemp indicates that the 
males average decidedly larger than the females, a point 
which it is not always easy to determine owing to the great 
difficulty in this genus of deciding as to the age of individual 
specimens. 
The genus Ctenomys, as a whole, is remarkably uniform in 
superspecific characters, and I find it impossible to subdivide 
it in any way, with the one exception that Ct. leucodon, 
Waterh., of the Bolivian Plateau, differs so much by its 
practically unpigmented incisors'and the extent to which they 
are thrown forward (angle about 118°, the majority of the 
species being about 10U° or, at most, 11U°) that it apparently 
deserves subgeneric distinction. I would suggest for the 
new subgenus the name of Haptomys. 
Reithrodon cuniculotdes pampanus, subsp. n. 
General essential characters as in cuniculoides of the south, 
not as in the more northern typicus. Body-colour of the 
same greyish olivaceous as examples from the Valle del Lago 
Blanco which I assign to hatchert, Allen, but fur rather 
shorter. Feet smaller, slenderer, and less heavily furred, 
though the terminal part of the sole is not so naked as in 
typicus. Tail well-furred, as in the southern form, but less 
