MUS. 143 
2. H. leucopus. Above varying from fawn shaded with black to lead-grey ; lower 
parts and feet pure white. Average length 3-25, of tail 2’80. 
3. H. aureolus. Above reddish fawn, passing below into pale fawn or yellowish 
white. Average length 3”, of tail 3’-60. 
4. H. californicus. Fars and tail very long. Above brownish grey, slightly 
washed with fulvous on the flanks; beneath greyish white. Average length 
about 5”, of tail 4-90, of ear 0°70 to 1”. 
5. H. aztecus. Above rich rufous, shaded with black along the back; lower parts 
and feet almost pure white; tail nearly naked. Average length 3:35, of 
tail 4"-08. | | 
6. H. mexicanus. Above dark grey, more fulvous on flanks, with a silvery lustre ; 
lower parts white or greyish white, sometimes washed with fawn. Average 
length about 4/20, of tail 3°20. 
7. H.melanophrys. Above lustrous grey (as in the last species); lower parts white, 
“edges of the eyelids and a small anteocular spot jet-black.” Average 
length 4", of tail 4°80. 
B. Nycromys, de Saussure, Rev. et Mag. de Zool. 1861, p. 106 (= Myoxromys, Tomes, 
P. Z. 8. 1861, p. 284). Form Dormouse-like. ars large; feet very short 
and broad; tail long, fully haired and pencilled. Skull short and broad, with 
well-developed supraorbital ridges. 
8. H. sumichrasti. Above bright rufous, beneath pure white, a black line or spot 
in front of the eye; tail blackish. Average length 5"-10, tail 5°50. 
C. Oryzomys, Baird, Mamm. N. Amer. p. 458 (1857). Form Rat-like. Ears small, 
hairy; hind feet large, with naked soles; tail moderate, either scantily haired 
or almost naked. Skull with marked supraorbital crests. 
9. H. palustris. Above greyish brown, passing into dirty white beneath ; tail 
scantily haired above, more. fully below; fur coarse and glossy. Average 
length 4°50, of tail 4”°50. 
10. H. couest. Above clear reddish brown, passing into dirty white or light fawn 
below; tail almost naked; fur close and woolly. Length about 5”, of tail 
5!""70. 
D. Tytomys, Peters, Monatsb. Ak. Berl. 1866, p. 404 (=Neomys, Gray, Ann. & 
Mag. Nat. Hist. 4th ser. xii. p. 416, 1873). Ears rather large, naked; soles 
naked. Skull with no raised supraorbital ridges, but with a broad horizontal 
edge over orbits; anteorbital foramen not visible from'above. 
11. H. nudicaudus. Above yellowish brown, mixed with black, beneath ochreous- 
yellow ; chin, breast, and median line of belly white; tail blackish at base, 
the terminal half white. Length about 7'-85, of tail 8'"30. 
12. H. panamensis. Above mouse-grey, beneath white; tail blackish at base, the 
terminal third white. Length about 8°50, of tail 8”. 
