2 University of Michigan 
stant advice and assistance is the reason behind its producion. 
The writer did the detailed work and the drawing, and an; 
‘naccuracies or errors of judgment that may appear can safely 
be laid to him. The drawing and photography were done at 
the zoological laboratory of the University of Pennsylvania. 
‘ _vcauied . uay of the environment of the region has 
already been published,’ it is only necessary, in this paper, to 
present again the location of the region and to summarize 
hrieily the ecological habitats. 
LOcATION 
All of the collection was made on or within a few miles of 
the Hacienda de Cuatotolapam, except one day’s work at the 
Laguna de Catemaco, about twenty miles away. The hacienda 
(map in Ruthven’s paper; /. c.) lies between the Rio San Juan 
and the Arroyo Hueyapam, a tributary, in the Canton of Aca-— 
yucan, southern Vera Cruz. This is approximately 18° N. 
Latitude and 95° W. Longitude, and about 50 feet above sea- 
level. The country is quite typical of the tropical lowlands, 
and the collections were made during what is known as the 
wet Season. 
The Laguna de Catemaco is a few miles to the north in the 
heart of the coastal San Andreas Tuxtla range, and not fat 
fromthe city Vf Gan Andreas Tixtla_ This lake also drains 
into the San Juan River system. ‘The range anu «_ a1, 
basin appear to be of volcanic formation. The altitude of the 
latter is not definitely known to me, but is probably not more 
than 2000 feet above sea-level. From the appearance of this 
region, a considerable difference in the molluscan population 
1 Ruthven, A. G., 1912. The Amphibians and Reptiles Collected 
by the University of Michigan-Walker Expedition in Southern Vera 
Cruz, Mexico; Zool. Jahrb., XXXII, abt. f. Syst.; pp. 295-330; pl. vi-x1. 
