■Occasional Papers of the Museum of Zoology 3 



would probably be found, but the visit was too short to ascer- 

 tain the fact. 



EcoiwOGY 



Here is simply included a brief classification of the habitats, 

 which is practically that of Ruthven {I.e.), 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: (aj 

 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 (juardas 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. 



IW Savannah grassland. The grazed, prairie-like portions, 

 probably due to disturbance by man and cattle. They are 

 practically without molluscan life. 



