666 ZOOLOGY. 
that a few of the Echinoderms belong to genera which flour- 
ished in the Cretaceous Period ; so that in a sense the abys- 
sal fauna may be said to be an extension in time of the 
Cretaceous fauna; the physical features of the deeper parts 
of the sea having remained nearly the same, while the 
shallower parts have risen and fallen so as to undergo great 
changes, and have wrought corresponding changes in the life 
along the shores of the continents. 
The following tabular view of the chief zoological faunas 
of the earth, proposed by Mr. J. A. Allen, is based on a 
study of the mammals, but will primarily apply to most 
land animals. The arctic realm is most distinctly charac- 
terized by the distribution of marine invertebrates, where 1t 
becomes of primary value : 
I. Arctic realm, undivided. 
II. North Temperate realm, with two regions, viz. + 
1. American region, with four provinces, viz.: 
a. Boreal. 
b. Eastern. 
c. Campestrian, 
da. Pacitic. 
2. Europxo-Asiatic region, also with four provinces, viz. t 
a. European. 
b, Siberian. 
c. Mediterranean. 
d, Manchurian. 
III. American Tropical realm, with three regions, viz. : 
1. Antillean. 
2. Central American, 
3. Brazilian. 
TV, Indo-African realm, with two regions, viz. * 
1. African region, with three provinces, viz. ; 
a, Eastern, 
b. Western, 
c. Southern. 
