90 
MAMMALIA. 
Trichecus rosmarus. — The Morse, or Walrus. 
Plate XVI. fig. 5. 
Lips very thick, beset with long strong ridged bristles ; fur 
thin, short, reddish ; two very large tusks, bent downwards and 
inflected. From sixteen to eighteen feet long. Inhabits the 
Northern Ocean. 
ORDER V.—MARSUPIALIA. 
In the sub-divisions of the different genera, the teeth vary 
considerably. The young are all produced prematurely, or in 
an early stage of developement, and become attached to the 
teats of the female, where they remain till they are fit to pro¬ 
vide for themselves. The mammae are situated in the abdomi¬ 
nal region, usually within a pouch, or fold of the skin, which 
serves as a protection to the young. This pouch is supported 
by two marsupial bones: thumb of the posterior extremities 
mostly distinct and opposable to the fingers; it, however, is 
wanting in a few species. 
Almost all the species are inhabitants of New Holland and 
South America. 
Division I. 
Having canine and insectiverous cheek teeth or grinders. 
Genus 1 . —Didelphis.— Linnceus. 
Generic Character .—Incisory teeth ^ canines J—J, grinders 
7I7 or 7I7 > total 48 or 50. The two intermediate incisors in 
the upper jaw longer than the rest, and separated from them ; 
they are very small and equal in the lower jaw ; the canines are 
strong, compressed, and somewhat reflected; the three first 
grinders in the upper jaw are false teeth, small and triangular; 
the remainder are insectivorous, or furnished with sharp points ; 
the four first in the under jaw are also false and small ; and the 
