lists of specimens examined, Nelson (_op. cit._:42 and
44) assigned certain specimens from "mountains near Santo Domingo"
and Guichicovi in Chiapas, and Catemaco in Veracruz, to _S. a.
aureogaster_, and other specimens from the same localities to _S. a.
hypopyrrhus_. I originally attempted to study (identify to subspecies)
the series of animals from only three places, but it became evident
that a more extensive study was indicated.

The locality whence the holotype of _Sciurus aureogaster aureogaster_
was obtained is unknown. Because certain specimens from Altamira,
Tamaulipas, closely resemble Cuvier's figure of the type, Nelson
(_op. cit._:41) subsequently designated Altamira as the type locality.
Miniatitlan, Veracruz, was designated by Nelson as the type locality
of _S. a. hypopyrrhus_ because Wagler's description of the type of
that subspecies fitted so well certain of Nelson's specimens from that
place.

_Sciurus a. hypopyrrhus_ was said by Nelson (_op. cit._:43 and 44) to
differ from _S. a. aureogaster_ in darker color, thinner pelage, much
stiffer and more shining dorsal hairs, slenderer tail with black
predominating, larger and proportionately narrower skull with larger
auditory bullae, each bulla being "slightly constricted just in front
of middle." _Sciurus aureogaster_ varies greatly in intensity of color
and in color-pattern. Fully 30 per cent of the specimens examined are
in some degree melanistic and approximately 20 per cent of them are
completely so. Others are more or less brown; the brown dulls the
usually rufous parts. In many specimens this brown is well distributed
even in the otherwise grizzled areas; in some specimens it is evenly
distributed and in others it is in patches. Indeed, scarcely any two
"normally" colored specimens are alike. Typically, the intense rufous
color characteristic of the underparts in both _S. a. aureogaster_
and _S. a. hypopyrrhus_ is also present on the costal region and
shoulders. Even this distribution of color is highly variable; some
specimens (for example No. 23948 KU, from 3 km. E San Andres Tuxtla,
Veracruz) show no rufous dorsally and others (for example No. 19307
KU, from 20 km. W Piedras Negras, Veracruz) have the rufous extending
over the legs, sides, and almost all of the dorsum from the shoulders
to the rump except (in some) for an interrupted median strip of
grizzled gray. It is true that specimens from Miniatitlan are darker
than those from Altamira, bu