Comparisons.—Differences from P. s. setosus are given in the account of that subspecies.
Remarks.—According to [Lund], these animals are found in the vicinity of small pools, swim well in spite of not having webbed toes, at night go after food and climb the corn stalks, and have their nests in the grass at the margins of the pools.
Specimens examined.—Total number, 2 (UZM), from Brazil, Minas Gerais, Nova Lima, Lagoa Santa.
Proechimys albispinus (Is. [Geoffroy])
General characters.—Size small; tail of same length as head and body or slightly less; feet small; ears of medium size; color of upper parts Ochraceous-Tawny gradually changing to Ochraceous-Buff on sides; differentiated, light-colored aristiforms on back, sides, rump and at base of tail; clavate aristiforms on back with Ochraceous-Tawny or Ochraceous-Buff, subapical zone; underparts of body and inner sides of legs white; tail blackish above, white below, with no white tip; hands and feet white on dorsal parts and some specimens darker on outer margins of feet; skull short and smooth, somewhat flattened in frontal region; jugal dorso-ventrally wide and with moderately conspicuous transverse ridge; postorbital process of zygoma well developed and involving both jugal and squamosal; bullae large and smooth; incisive foramen short and narrow; vomerine sheath incomplete or complete; molariform teeth with only one counterfold; incisors orthodont or proodont.
Remarks.—A good series from Macaco Seco, Andaraí, Bahia, agrees closely with the form first described (albispinus) from the Island Madre de Deus, in Todos os Santos Bay, Bahia. Compared with topotypes of P. albispinus sertonius, the animal from Macaco Seco in general color is more Ochraceous-Tawny and has a narrower skull with orthodont incisors. Specimens from Bonfim, northeastern Bahia, on the other hand, agree with [Thomas'] albispinus sertonius, from Lamarão, being browner and having broader skulls than P. a. albispinus and having proodont, instead of orthodont, incisors. The range of each of the two subspecies is, therefore, fairly extensive. The insular form extends to the less rainy, continental area and the form from Lamarão ranges northward (NNW) in the same type of highly deciduous forest, the "caatinga."
The species albispinus is certainly the most specialized form of the entire genus for drier habitats. In addition to the general adaptations described above, it is noteworthy for having both lanceolate and clavate aristiforms. The latter type has a wide basal part and an abruptly narrowed, distal part. The same development is seen in the genus Echimys, where highly spinous forms, like Echimys paleacea ([Lichtenstein]), show the same two types of aristiforms.
