Occasional Papers of the Museum of Zoology 2 
would probabiy be found, but the visit was too short to ascer- 
tain the fact. 
FcoLocy 
Here is simply included a brief classification of the habitats, 
which is practically that of Ruthven (J.c.), where the details 
are presented and illustrated by photographs. A review of 
the molluscan inhabitants of the various environments will be. 
given in another paper. 
A. Terrestrial Habitats. 
I. Lowland forests. The dense jungle of the untouched 
flood-plains. Two ecological strata are recognized here: (a) 
the ground stratum, which includes the leaf-humus, rotting 
logs, and other debris; and (b) the arboreal or subarboreal 
stratum, under which are taken up the species obtained from 
the trees and bushes themselves, both from the leaves and the 
trunks. 
II. Lowland forest clearings. These may be subdivided into 
. three classes: (a) partially cleared places along the Arroyo 
Hueyapam (bush and a few clumps of large trees) ; (b) the 
burnt-over ground (mainly dead shells obtained); and (c) 
cleared fields (the fields of sugar cane and corn and the roads 
and guardas rayas between them). 
III. Savannah forests and thickets. Clumps of bush and 
relict jungle, usually on higher ground, and of a more xero- 
phytic type. The yuccas and spiny palms are especially prom- 
inent, scattered in clumps through the mesophytic vegetation. 
The ground stratum (a), and the subarboreal stratum (b), 
may also be recognized here. 
IV. Savannah grassland. The grazed, prairie-like portions, 
probably due to disturbance by man and cattle. They are 
practically without molluscan life. 
