C. H. TYLER TOWNSEND — BIOGEOGRAPHY OE MEXICO, ETC. 47 
rect, and is adopted in this paper. Whether there is another fauna in 
this Gulf coast region, between the Tamaulipan and the Yucatecan, 
remains to he seen. If so, it must appear at its best in the State of 
Tabasco, and will take its name therefrom. A contemplated trip to that 
region, which the writer proposes soon to set out on, for the purpose of 
making much more extensive collections than heretofore, will, as soon 
as the collections are worked up, at once decide the point as to the affini- 
ties of the fauna and flora of Tabasco. 
It may he said in general that the surface of Yucatan consists, for the 
most part, of limestone rock covered with a very scanty soil. The rock 
crops out constantly on the surface. The henequen plants thrive in this 
soil, which, without good rainy seasons, or artificial irrigation, will not 
produce any other crop. There are no surface streams in Yucatan, hut 
subterranean streams flow beneath all this country, so far as can he 
judged. The only water to he found on the surface in the dry season 
is that contained in large holes known as cenotes tod aguadas. A cenote 
is considered to he an opening to an underground river. A brief de- 
scription of the first cenote of Xcolak (a Maya word pronounced schko- 
lack, with a strong gag-like delivery on the first Tc , a holding of the o , 
and a strong accent on the last syllable) will give a correct idea of most 
of them in the dry season. 
What looks like a circular pond of slightly greenish water, about 150 
feet in diameter, is seen lying at the bottom of a sudden depression in 
the surface of the ground, in the midst of the dry and dusty woods. 
Everything around looks dry and parched, except a little green vegeta- 
tion on the hanks encircling the water. Even the water presents a stale 
appearance, and does not seem capable of reducing the thirst caused by 
the intense heat. Its surface is sluggish and motionless, and hears par- 
ticles of moss or algae floating on it or suspended within it. The water 
is about ten or twelve feet below the surface of the surrounding county 
and the hanks surrounding it are steep. On the southwest side the water 
can he waded into for a short distance, hut one sinks up to his knees in 
the soft mud or debris. On the north side the hank comes down more 
abruptly, and the water goes down sheer at the edge. These cenotes are 
said to have no bottom, some of them having been sounded with long 
lines without finding bottom. Dr. George E. Gaumer, of Izamal, told 
the writer that he had on several occasions tied a long line, with a lead 
sinker on the end, to a piece of cork used as a float, and placed it in the 
water at the south end of a cenote, when the cork would invariably 
slowly float across the surface to the north edge, although the water was 
absolutely quiet; thus indicating a current deep down, always from south 
to north, acting on the lead sinker. Erom these observations Dr. Gau- 
mer concludes, and I think with good reason, that these cenotes are the 
