Edward's Massasauga

Sistrurus catenatus, variety edwardsii, (B. & G.)

Dimensions: Like the typical form.
Distribution: The range of this variety begins from the extreme southern distribution of the typical form and extends from the Indian Territory, throughout western Texas, and westward to about the central portion of southern Arizona. It also occurs in northern Mexico, adjacent to the boundary.
Habits: It seems that this reptile is less partial to damp situations than the preceding form.
Distribution: Southeastern U. S.
Distribution: Texas to southern California.
Distribution: Southern and Lower California.
Distribution: Southern California, Lower California and Arizona.
Distribution: Arizona, New Mexico and Mexico.
Distribution: Central United States; Canada to Mexico.
Distribution: Extreme Western States.
Distribution: Arizona and Mexico.
Distribution: Deserts of Arizona, Nevada and California.
Distribution: Eastern United States, Vermont to Florida; westward to the Plains.
Distribution: Desert mountains of Southern California, Arizona and Nevada.
Distribution: Region of the Mexican boundary--western Texas to western Arizona.

This variety is distinguished by the much paler--yellowish--ground-colour and the smaller spots on the back. The spots on the sides are indistinct. In miniature, the pattern of this snake is much like that of the prairie rattlesnake, (Crotalus confluentus).

While the typical form has twenty-five rows of scales, this variety has but twenty-three.

From all of the other rattlesnakes of the Southwest, it may be instantly told by the large plates of the head.

The Rattlesnakes--Crotalus: The present genus embraces the Rattlesnakes proper. The species may be recognised from the preceding genus of small Rattlesnakes by the scalation of the head; this small and granular. A few of the species have small shields on the forward portion of the snout--in front of the eyes.

Fifteen distinct species and several varieties of Crotalus are known. Eleven of the species and two varieties are found in the United States. Concerning the latter, a key is given:

Division I. A chain of large, dark, pale-bordered rhombs--"diamonds."

a. Diamond markings closed on sides.

Dagger Size large.

Dark olive; rhombs with yellow borders.

DIAMOND-BACK RATTLESNAKE, C. adamanteus.

Grayish; rhombs with whitish borders.

WESTERN DIAMOND RATTLESNAKE, C. atrox.

Reddish; rhombs with whitish borders.

RED DIAMOND RATTLESNAKE, C. atrox variety ruber.

Dagger Size moderate.

Dull white or pinkish, with very obscure, rhomb-like markings.

WHITE RATTLESNAKE, C. mitchellii.

b. Diamond markings narrowly open at sides and continued downward as narrow bands.

Yellow or greenish. Two paler blotches within each rhomb.

BLACK-TAILED RATTLESNAKE, C. molossus.

Division II. A row of rounded, dark-bordered blotches, well separated.

a. No horn over the eye.

A pale band, one scale wide, in front of eye.

PRAIRIE RATTLESNAKE, C. confluentus.

A pale band, two scales wide, in front of eye.

PACIFIC RATTLESNAKE, C. oregonus.

Dagger Size small.

Two rows of blotches on forward portion, fusing into a single row in rear of body.

PRICE'S RATTLESNAKE, C. pricei.

b. A horn over each eye.