522 On Didelphys waterhousei, Tomes. 
postorbital projection 8°6 ; maxillary tooth-row 15:3; three 
anterior molariform teeth 6:5. 
Hab. W. Ecuador. Type from Santo Domingo, 0° 13’ S., 
1 OG! AVS, ANE UDO 
Type. Old male. B.M. no. 15.1. 1.54. Original num- 
ber 424. Collected 19th July, 1914, by Gilbert Hammond. 
Presented by Oldfield Thomas. Four specimens. ’ 
This Marmosa is remarkably like the Trinidad M. chap- 
mani, but no species similar to it seem to have been recorded 
from west of the Andes. Its large size, long feet, and 
general robust build all make it resemble I. chapmani, from 
which it differs by its smaller ears, more naked tail, and 
normal-shaped canines, apart from the very wide difference 
in locality. 
Note on Didelphys waterhousei, Tomes. 
In his recent important work—‘ Genera Mammalium ’? *— 
Sr. Cabrera has placed my Marmosa germana, from the Oriente 
of Ecuador, as a synonym of Tomes’s waterhouset, supposing 
the latter, like germana, to be a member of the cinerea group. 
This mistake has naturally arisen from the carelessness with 
which Tomes allowed a figure of Waterhouse’s specimen to 
be published as his D. waterhousez, when at the same time he 
was describing under that name the skin brought home by 
Fraser from Ecuador. Now the two animals are really 
totally different. Waterhouse’s specimen was an immature 
specimen without locality, but clearly a real grey opossum 
of the eénerea group. It is still in the Museum, and bears 
the number 42. 4. 29. 70, but is indeterminable with any 
further exactitude. ‘The true waterhouse?, however, as based 
on the Ecuador skin, is quite of a different group, as may be 
seen by the figure of its skull published on p. 303 of the 
same volumet in which the species was described. ‘This 
skull, now in the Museum (no. 7. 1. 1. 215), has no resem- 
blance to that of any member of the cémerea group, though, 
unfortunately, owing to the disappearance of the type-skin,. 
I am for the present unable to identify it more exactly. 
Although with unusually well-developed postorbital pro- 
cesses, it would appear to belong to the murina group, to 
whose members its colour, as described by Tomes, indicates 
considerable resemblance. 
Whether the ordinary Keuadorean species of that group— 
a form nearly related to Mf. mitis—ever develops such pro- 
cesses I do not know, but in any case further material will 
* P. 39 (1919). 
+ P. Z. 8. 1860. 
