In discussing the type locality of the species, [Thomas] (1921:141) states: "We know that its donor did obtain a number of specimens from Rio Janeiro, and the skull agrees so closely with those of two examples from Itatiaia, near to the Rio-Minas frontier, collected and presented by Prof. J. P. Hill, that I have no hesitation in referring the latter to Günther's species."
Specimens examined.—Total number, 211 (MN), from Brazil as follows: Rio de Janeiro; Parati, Pedra Branca (400 m.), 113; Mangaratiba, Fazenda do Rubião (750 m.), 3; Fazenda do Tenente (700 m.), 4; Fazenda da Lapa (450 m.), 13; Teresópolis, Fazenda Guinle (960 m.), 61; Nova Iguassú, Barro Branco (20 m.), 16; Distrito Federal, Tijuca, 1.
Additional records.—Rio de Janeiro, Itatiaia ([Thomas], 1921:141); Rio de Janeiro, Zona da mata, Mont-Serrat, Serra do Itatiaia ([Ribeiro], 1905:187).
Proechimys iheringi [Thomas]
General characters.—Size large; tail long; aristiforms generally wide and stiff; general color on upper parts and sides a combination of blackish from tips of aristiforms with cinnamon ground color from subapical zones of setiforms; darker band on middorsal line; differentiated light-colored aristiforms conspicuous on outer sides of thighs and rump; usually rufous tint on neck and postauricular region; underparts white; tail with white tip, usually accentuated by white brush; feet white on dorsal surface; hind feet slightly darker on outer sides; skull elongate and smooth; jugals wide dorso-ventrally; incisive foramen elongate; upper molariform teeth usually with one to five counterfolds, number varying with subspecies; lower premolar always with two counterfolds and lower molars always with one or two counterfolds.
Remarks.—As a whole, the samples of the populations of the species do not afford a satisfactory record of the distribution; my concept of the group may be changed when further collections are made in localities geographically intermediate between those from which specimens now are known. If some of the forms prove to be physiologically isolated, they may deserve treatment as full species according to the conventional standards of systematic zoology. P. panema, for example, does not seem to be geographically isolated from P. gratiosus. P. denigratus, at the northernmost known occurrence of the species, actually represents a striking jump in the cline, although collections from intermediate regions may provide intermediate structural stages. Further collecting may also prove that the southern form, P. iheringi iheringi, is completely isolated from the rest of the group. However, these samples are certainly more related to each other than any one of them is to that of the other species found in the same range, namely P. dimidiatus, and all the forms in question, therefore, seem best arranged as subspecies of one full species. A clinal variation certainly exists among these forms and the most striking differences correspond to larger geographical distances.
Fig. 104. Proechimys iheringi iheringi, female, MN no. 6453, Ilha de São Sebastião. × 1.