206 Ml-. O. Thomas on small Mammals , 



tliese specimens tlieiefoie, wliatever other co-types were 

 mixed up Avith them, being able to be taken as lectotypes of 

 their respective Jiames. 



Now over most of the area concerned we seem to have two 

 quite distinct forms of Akodoti — A, with a short, normal- 

 shaj^ed, rather bowed skull, on whose m^ a very distiact and 

 fairly persistent anterior median notch is present, an animal 

 externally lined gre3'ish brown, wirh a contrasted white chin- 

 spot, and B, with a flattened long-nosed skull, the jti^ practi- 

 cally without a notch, this oidy being perceptible in an 

 aborted form in specimens with quite unworn teeth. Exter- 

 nally this animal is greyish or yellowish, with the feet more 

 distinctly yellow, and t!ie chin-spot not contrasted. 



Returning to the type-specimens, it is quite clear, as shown 

 by their skulls and teeth, tiiat both 55. 12. 2-1. 156 and 157 

 belong to B, and that therefore A is without a name. Young 

 and supplementary specimens obtained by Darwin on the 

 Rio Negro and at Port Desire are referable to A, but these 

 do not affect the determinations, and I propose to give to the 

 latter form the name of A. iniscatus. A local form of it, 

 obtained by Sr. Budin, I now describe.] 



11. Ahodon iniscatus colUnus^ subsp. n. 



<J . 205, 208, 209, 210 ; ? . 206, 207, 218. Maiten, 

 W. Chubut. 700 m. 



A more blackish race of A. iniscatus. A full description 

 is given here instead of to the typical iniscatus, as quite fresh 

 specimens are available of it, while those of that animal are 

 less perfect. 



Size small, about as in xanthorhinus and canescens, the 

 tail short as in those southern species, not as in the arenicola 

 group. General colour above dark grizzled olivaceous brown 

 {more greyish olivaceous and less brown than Ridgway's 

 *' olive-brown"), the hairs ticked with black and dull bufFy ; 

 sides rather more buffy. Under surface soiled greyish buffy, 

 the hairs dark slaty at base, their ends drabby or bufty — a 

 patch in the inguinal region more definitely bufify. Chin, or 

 rather interramia, with a conspicuous patch of wholly white 

 iiairs, contrasting markedly with the general dark colour. 

 Ears short, their proectote blackish, their metentote buffy. 

 Hands and feet brownish white. Tail short, well haired, 

 strongly bicolor, black along the top, whitish or buffy whitish 

 on sides and below. 



Skull rather bowed above, its surface smooth and unridged. 

 Interorbital edges square, not ridged. Palatal foramina long, 



