MAR8UPIATA. 
9 
frequently a band or projecting ridge, more or less perfectly 
encircling the tooth at the baso of the exposed portion, and 
this band throws up small tubercles in parts; frequently on the 
outer sido of the tooth a small tubercle is thrown up from the 
anterior angle of the tooth, a second tubercle in the middle, 
and a third at the posterior angle. By the development or 
non-development of one or more of these parts, most of the 
varieties observed hi complicated molar teeth may be ex¬ 
plained; and in my descriptions I shall endeavour to trace 
and point out these modifications in the different genera. 
Of the affinities of the various minor groups of which the 
order Marsupialia is composed, with the exception of one or 
two cases, there can be very little difference of opinion ; the 
modifications of die extremities, combined with die diameters 
furnished by the digestive system, very clearly indicate the 
natural divisions, and their relationship to each odier. 
In die structure of the stomach, Professor Owen points out 
diree leading modifications 1 ; it is simple in the genera 
Didtljihys , Mt/rm< eobiuA. and Peramek* , and likewise in the 
Diuyurns and PhalangUta groups; also simple in the Koala 
and Wombat, hut in diese two animals it is provided with a 
glandular apparatus situated to the left of the cardiac orifice ; 
the diird modification is exhibited in the Kangaroo section, 
where it is complicated by sacculi. The small intestine com¬ 
mences with a coecuin in all die groups with the exception of 
the Datyuridw; die ccecum, according to Professor Owen, is 
moderately long in the Myrmccobiu * , Ptrame/es , and Didcl- 
p/iys, very long in the Phalavgist idas (including the Koala), 
long in die Macroj)odid<r y and short, wide, and with a vermi¬ 
form appendage, in the Wombat. Setting aside the Mono- 
tremes, we find one type of dentition exhibited in the car- 
1 See the article M Marsupialia,” in Todd’s Cyclopedia of Anatomy and 
Physiology. 
