FROM TEXAS AND MEXICO. 121 



decreases gradually, until in old snakes the addition during 

 the time of producing a ring is hardly perceptible. In the 

 time from the completion of the fifth ring to that of the 

 sixth only a couple of inches were added on our examples. 

 My means of determining the time required in the pro- 

 duction of a ring have not been wholly satisfactory. Liv- 

 ing individuals certainly acquired a ring at the time of 

 sloughing in the spring. Of about seventy alcoholic spec- 

 imens collected between May and September each of three, 

 secured late in the season, shows a new button well under 

 way ; proving that at least in cases a ring is added in the 

 fall. The general opinion is that only one ring is grown 

 each year. To take one per year tis the ordinary rate gives 

 G. atrox, from Dr. Palmer's specimens, about seven years 

 in which to finish the strongly tapered portion of the rattle, 

 becoming full grown in a total length of not fur from three 

 feet six inches. An individual four feet in length has seven 

 of the equal rings, having lost all the tapering; this, at a 

 ring per year, would indicate an age of fourteen years or 

 more. Other snukes slough both in spring and fall. The 

 few observations I have been able to make at the proper 

 seasons go to show the rattlesnakes possessed of the same 

 habit. If this be so and a ring is gained at each slough- 

 ing, as seems to be the case, the number of the years of 

 the snake will be but half as large as that of the rings. 



o o 



The male in this and the following species is generally the 

 smaller for the same number of rings. 



In connection with the foregoing a number of specimens 

 of each of several other species have been examined, with 

 a view of determining how much stress may be placed on 

 the conclusions suggested above. On account of the great 

 amount of individual variation from sex, locality, food, 

 etc., it is necessary throughout to speak in terms of aver- 



