222 PROCEEDINGS OF THE NATIONAL MUSEUM vol.93 



of the land. The crater is approximately l 1 ^ miles across from east 

 to west, and about a mile in the opposite direction. Carriker thought 

 the depth to be about 800 feet, and noted two small vents, with minor 

 cones and craters, rising from the floor. These were forest covered. 

 One small area on the main crater floor, of perhaps 10 acres, was almost 

 bare of vegetation, having only a few scattered trees. Collecting here 

 continued until April 22. 



On the return journey to Tres Zapotes, Carriker crossed from 

 Santiago de Tuxtla to Lirios instead of making the long circuit to 

 Tapacoyan. The trail though rocky and broken in places was easily 

 practicable in the dry season, but probably not feasible during the 

 rains. 



On May 13 Carriker returned to Tlacotalpam and made another 

 visit to El Conejo on May 15; he collected near the town on May 16 

 and 17, when field work for the season came to an end. 



PHYSIOGRAPHY AND LIFE ZONES 



Except for limited areas, the region covered in this report lies 

 in the Humid Division of the Tropical Life Zone. At Tlacotalpam 

 the land is almost at sea level (pi. 26, fig. 1) , the effect of tide is felt 

 in the rivers, and there are extensive swamps. Near Tres Zapotes the 

 terrain becomes slightly undulating, with an average elevation of 

 about 200 feet, rising steadily with more broken aspect toward the 

 Sierra de Tuxtla (pi. 28, fig. 1). This range has four main peaks, the 

 highest being Volcan San Martin. According to an account by Im- 

 manuel Friedlaender, 1 San Martin rises to 4,600 feet (1,400 meters) , 

 but Carriker's barometer readings showed about 5,500 feet. The 

 Cerro de Tuxtla (called by Friedlaender C. Santiago) is about 4,000 

 feet (1,200 meters), and Cerro Prieto (Mono Blanco of Friedlaender) 

 about 3,800 feet (1,150 meters). The Cerro Vigia, a spur of San 

 Martin, is about 4,100 feet. (The difference in names for these indi- 

 vidual mountains is due apparently to local usage, as Friedlaender 

 worked from San Andres Tuxtla at the east, while our contacts were 

 with people living to the west and north.) 



The Arid Division of the Tropical Zone surrounds the humid low- 

 land area of the Tuxtla region, with savannas cutting in irregularly 

 on the forests around their borders. According to the manuscript 

 notes of E. W. Nelson in the files of the Fish and Wildlife Service, 

 arid conditions come in south of the Tuxtla range at the western 

 side of Lake Catemaco, where the low hills and valleys are dry, with 

 sparse, woody vegetation. 



1 Tiber das Vulkangehiet von San Martin Tuxtla in Mexiko. Zeitschr. fur Vulkanologie, 

 vol. 7, No. 3, Nov., 1923, pp. 162-173, pis. 17-24. 



