Didelphidje. MAMMALIA. Didelphid.e. 217 
is widely distributed throughout the United States, and 
is especially abundant towards the south. A full-grown 
specimen measures twenty inches in length, exclusive of 
the tail, for which other fourteen inches must be allowed. 
The fur has a dusky-brown colour, the individual 
hairs being whitish, with brown tips. The legs are 
nearly black, the digits being lighter coloured or whitish. 
The head is fulvous-white, with a dusky suffusion round 
the eye ; the ears are black, with a yellow patch at the 
upper border; the root of the tail is also dark coloured. 
The Possum is Very destructive to poultry, and proves 
a troublesome pest. The female produces sometimes 
as many as sixteen young at a birth, which, when at 
first transferred to the marsupial pouch, are extremely 
minute. The ej''es of the young open about the fiftieth 
day, when the cubs are as large as ordinary mice. 
The flesh is said to be good eating. 
Among the more interesting or noticeable of the 
other species, we may mention the following The 
Texas Possum {Didelphis Californica), which is dis- 
tinguished by its smaller size, its less rounded and 
more pointed ears ; the hairy or basal portion of the 
tail being also shorter. According to Mr. J. H. Clarke 
of the United States expedition, this species is parti- 
cularly fond of the black persimmon, an abundant fruit 
Fie:. 
on the borders of the Eio Grande. The D. Murhvi 
is found in Mexico, Guyana, Peru, and Brazil ; the D. 
dorsigera in Surinam. “ These species,” as Van der 
Hoeven observes, “ carry their young on the back when 
they are sufficiently developed to leave the teat, to 
which at first they were attached, whilst they throw 
their tails like tendrils round the caudal appendage of 
their parent.” In both the tail is fully as long as the 
body, and tbe ears are largely developed. Azara’s 
Possum (D. Azarce) pretty closely resembles the Texas 
form. According to Mr. Spencer F. Baird, it is distin- 
guished by its white head and neck, with a central dark 
stripe along the forehead to the dusky part of the nape. 
The ears and toes are flesh-coloured. The Crar- 
EATiNG Opossum {D. cancrivord) — so called from its 
propensity for eating these Crustacea — is a large spe- 
cies, possessing no well-defined markings on the head; 
the generically distinctive, long, and sparsely scattered 
hairs of the short fur existing more or less abundantly 
in all the opossums. The fur exhibits a deep black 
colour. 
THE YAPOCK {Cheironectes variegatus), or Petite 
Loutre of Buffon, is an aquatic form of opossum 
inhabiting the river banks of Brazil and Guyana (fig. 
92). The only point in which it appears to differ 
. 02 . 
The Yapock (Cheironcctes variegatus) 
materially from the ordinary opossums, has reference 
to the palmated character of the feet, which are 
supplied with interdigital membranes. In all other 
particulars it conforms to the genus Didelphis. The 
Yapock is little more than a foot in length, exclusive 
of the tail, which is scaly and prehensile, and nearly 
as long as the body. It is an expert swimmer, and 
feeds upon fishes, Crustacea, and other aquatic animals. 
Oeder XIV.— MONOTREMATA. 
It is not a little significant of the universality of plan 
pervading aU vertebrate formations, that we should 
find on examining the skeleton and viscera of the 
monotremes, a decided approximation to certain of 
VoL. I. 28 
the distinguishing characteristics of birds and reptiles. 
At first sight there is little to suggest this relationship, 
except in so far as the bill-like jaws of Ornithorynchus 
are admitted to resemble a duck’s beak : but on closer 
