C. H. TYLER TOWNSEND — BIOGEOGRAPHY OF MEXICO, ETC. 
67 
able than that of the United States immediately south of the Great 
Lakes. The lowest temperatures known on the high plateau of Arizona, 
bring less discomfort than a chilly day in Hew Orleans.” 
s 
GILA HEADWATERS. — The headwaters of the Gila consist of three 
branches or forks, which unite just above the Gila Hot Springs and thus 
form the Rio Gila. They are situated in the mountains of southwestern 
Hew Mexico, in northern Grant and southern Socorro counties. 
Diptera. — A first paper has been published in Psyche (1897, pp. 
38-41) on diptera collected in the Gila canons during the 1894 trip, the 
itinerary of which was given in the first paper on biogeography. Some 
further topographical notes on the district are given in the paper *in 
Psyche, The diptera so far determined by the writer are as follows: 
1. Chrysops ceras Towns, n. sp. — West Fork, July 10 to 17. Forms 
a group with C. megaceras Bell, of Mexico, and C. tanyceras OS. of 
Costa Rica. 
2. Chrysops facialis Towns, n. sp. — West Fork, July 19. 
3. Tabanus punctifer OS. — Head of East Fork, DD-Bar ranch, July 
22. An Upper and Lower Sonoran species. 
4. Tabanus gilanus Towns, n. sp. — West Fork, July 10 to 16. Seems 
more nearly related to T. rheinwardtii Wd. OS., of the eastern United 
States ( Carolinian and Appalachian ), than to other species. 
5. Tabanus intensivus Towns, n. sp. — West Fork, July 13 to 16. 
Closely allied to the preceding. 
6. j Eristalis latifrons Lw. and var. maculipennis Towns.— East Fork, 
July 22. A Transition and Upper Sonoran species, ranging into the 
Lower Sonoran apparently, judging from the localities Sonora and Mata- 
moros recorded for it. It is, however, a higher species, reaching its great- 
est abundance in the Transition. 
7. Chrysochlamys croesus OS.— West Fork, July 12. A Transition 
species. 
8. Zodion fulvifrons Say (typical form). — West Fork, July 18. This 
form seems to range higher than the variety abdominale Say, which is 
Upper Sonoran and Carolinian, apparently ranging into the Lower So- 
noran as far south as Guerrero (Biol 0. A. Dipt.). 
9. Dejeania corpulenta Wied. — We.st Fork, July 16. A Transition 
species, ranging but a short distance down into the Upper Sonoran, but 
considerably into the Boreal (Colorado). At the same time it extends 
southward to the higher mountains of Costa Rica, Panama, and Colom- 
bia, at from 4000 to 7000 feet. 
10. Myobia gilensis Towns, n. sp.- — West Fork, July 16. Allied to 
M. diadema Wd. and flavipennis Wd., of the Neotropical region. 
