226 DR. H. GADOW ON MEXICAN [June 6, 
VIPERIDZ.—CROTALIN®, taken together, occur all over Mexico,as 
is to be expected of a group which ranges from Massachusetts and 
British Columbia to Argentina, but they fall into two lots :— 
I. Northerners, with their archaic centre in Sonoraland. 
Ancistrodon is chiefly Nearctic; but of the terrestrial forms 
A, bilineatus extends along the Pacific side of Mexico, including 
Tres Marias Islands, to Yucatan and Guatemala. Of Sistrwrus, east 
of the Rocky Mountains, S. ravus has been deseribed by Cope 
from Vera Cruz. Crotalus, the main genus, radiates out from the 
tablelands of Arizona; C. terrificus (horridus of some authors) is 
the only species which extends right through Mexico to the 
Isthmus, and thence right into Argentina, avoiding, however, the 
moist and wooded Tierra Caliente. It is the only Rattlesnake in 
South America. C. iriseriatus is confined to Mexico’s mountains, 
ranging from the Nevado de Colima right across to Citlaltepetl, 
where I have found it at an altitude of 12,500 feet. 
Il. Southerners.—Lachesis, an essentially Neotropical genus, 
a few species of which extend into the Eastern and Western 
States below the plateau. JZ. lansbergi has the widest distribution, 
and it is the only Pit-viper which has entered the Lesser Antilles, 
the larger and older islands being free from poisonous snakes. 
The Rattlers, or ‘‘ Viboras de cascabél,” are not much feared, 
being ‘‘manzitos” (rather tame), meaning sluggish and not 
inclined to strike unless provoked; moreover, they always try to 
give fair warning with the rattle, which they sound only when 
coiled up and prepared to strike, but not when crawling away as 
they generally attempt doing. The Lachesis lanceolatus, the “ Fer 
de lance ” of Martinique, &e., ‘‘ Rabo de hueso” or Bone-tail of the 
Mexicans, on account of the curiously coloured and spike-like tip 
of the tail, behaves quite differently. It is very quick, highly 
irascible, and even known to make for its pursuer, therefore much 
dreaded. In fact the few cases of snake-bite which I could 
ascertain, mostly fatal, were due to this species. 
Résumé of the Distribution of Ophidia. 
Typhlopide.—Central and South American, Atlantic Mexican 
and Antillean *, 
Glauconiidee.— Remnants of Sonoran to Neotropical distribution; 
they may reasonably be expected to be found in the Antilles. 
Boide. 
1. Xerophile Sonoran, not Antillean. 
2. Hygrophile Central South American, Mexican Tierra 
Caliente, and Antillean. 
_ * For the present purpose only those Snakes are considered Antillean which occur 
in the Greater Antilles. The Lesser Antilles, entirely volcanic and of much younger 
date, have received the Lachesis, Oxyrhopus, and Glauconia directly from the opposite 
part of Venezuela. 
