C. H. TYLER TOWNSEND — BIOGEOGRAPHY OF MEXICO, ETC. 49 
A horsefly, taken in numbers on onr horses at Xcolak, proves to he an 
nndescrihed species, and I have named it Tabanus yucatanus. Moreover, 
it is the first recorded tabanid from Yucatan, so far as I know, which 
seems strange. A new species of scale-insect, found at Xcolak, has also 
proved to he of much interest, and has been named by Professor Cockerell 
Lecanium (. Eulecanium ) perditum. 
Four attid spiders, collected from the scanty green native vegetation 
at Izamal, in May, have been identified at the United States Department 
of Agriculture, by Mr. Banks, as follows: Zygoballus sexpunctatus 
Hentz; Zygoballus sp.; Dendryphantes nubilus Hentz; and Habrocestum 
probably n. sp. The trip from Vera Cruz to Yucatan was made under 
the auspices of the United States Department of Agriculture, in the 
interests of the Entomological Division. 
The Tabascan Fauna. — Since the foregoing was written, the writer 
has begun the work of making the Tabasco collections already referred 
to, and has spent two months in this work at Frontera. It is evident, 
from observations so far made and material collected, especially as re- 
gards mammals, birds, reptiles and insects, that there appears here an- 
other well marked fauna cropping out on the coast, between the Ta- 
maulipan and the Yucalecan. It should he known as the Tabascan 
fauna. Its details can he worked out only with the careful study of the 
collections when completed, hut it will doubtless he found to extend in 
general from the Coatzocoalcos river to central Campeche, taking in 
nearly all of Tabasco and the lowlands of northern Chiapas, and extend- 
ing across northern Guatemala to Belize. Nearly the whole of the State 
of Tabasco is composed of lowlands, which extend up the Usumacinta 
river to the Guatemalan frontier. Over this immense stretch of low, 
rich and well watered country, from the upper waters of the Rio Usuma- 
cinta down to the Tabasco coast, the tropical types of Central America 
have spread northward from eastern Guatemala and Honduras. While 
some extend on farther north through Vera Cruz, others reach their 
limit here, and thus a differentiated character is imparted to the fauna. 
This district is the most decidedly tropical ( Neotropical ), with all the 
attributes which the word implies, of all Mexico. The lowlands, between 
the mountains and the coast, are of much wider extent here than else- 
where on the Gulf of Mexico coast within the tropics, while the condi- 
tions of soil and climate are the most favorable for tropical life. The 
extensive lowlands, only very gradually rising, which stretch away into 
the interior up the Usumacinta to Guatemala, store up and retain the 
heat, and increase the annual totals of temperature control. At the same 
time they reduce the possibilities of low winter temperatures. Northers 
