MAR8UP1ATA. 
17 
sufficiently evident, a a it appears to roe, though not so striking as in the 
Marsupiata, but this may, I think, he accounted for. 
Let us compare the Mannpiata, und the sections of which it is composed, 
with the PlaoentAlia, in another point of view. In those groups which are 
universally admitted to he o rdera, there arc roost frequently very many species, • 
and, what appear* to me of more importance to notice, there nrv In each order 
many genera and » vcnl families. Sometimes, where an order doe* not contain 
many recent specie*, the comparatively few specie* present very striking modifi¬ 
cations of Structure, a* i» the ease with the order Edentata: here, however, we 
know that a great portion of the species liavc become extinct, at well at in the 
order Paehydermata t which presents a similar condition, having but few recent 
species, and those exhibiting striking modifications of structure: then, again, 
wc find that the groups admitted to be orders hare representatives in widely 
separated portions of the globe, and not only each order is widely disj>crsed, 
hut frequently the principal genera of which each is composed, and from which 
the other genera appear to radiate, have (or had) an almost universal distribu¬ 
tion 1 . Some orders do not present all these conditions, not containing •cveral 
genera of universal distribution, but all evince an approximation to them ; 
and it is amongst those orders which fall short (if we may so speak) of these 
conditions, that wc find the nearest approximation to parallelism to the Mart*- 
piata as regards geographical distribution. The Edentata , like the Marsupiata , 
are found in both hemispheres ; each of these divisions, however, has its chief 
metropolis in one hemisphere ; both, low in grade of organisation, arc driven 
down, os it were, into the southern portions of the globe, but have existed in 
former times in the northern hemisphere. Both include species exhibiting 
very marked variations in structure and of bahit*. But the Edentata are 
correctly, a* I think, regarded by most naturalists as forming an order. 
When, on the one hand, we find the conditions presented by the principal 
divisions of the Marsupiata approximate most nearly to those of families of other 
orders, being separated from each othrr by comparatively trivial characters, 
and that the whole group presents the strongest anology to other groups 
which are regarded as orders, with respect to tbrir geographical distribut ion, wc 
are warranted, eatrris paribus, in regarding the Marsupiata as an order. But 
then it may be said, perhaps, that the amount of differential characters which 
serve to separate the Marsupial!* from other orders b greater than that by 
which those orders are distinguished. If it be true that each minor group of 
1 In the order Carnivora we find (having a nearly universal range) the 
geaera Conor, Felts, Mustela, Ursvs , and Phoea ; in the Rodkntia, Scivrvs. 
Mm, Hystrir (Linn.) and Lepus in the Paciiydkrmata, Mastodon 
(fossil), Tapi ms (and its allies, found only in a fossil state), Equus (either 
recent or fossil), and Sus (Linn.) 
VOL. I. 
C 
