262 BULLETIN OF THE 
been set free with the first slough, holding only by the collar; and if 
the snake had been allowed to live a little longer, the second sloughing 
would have discovered the third button perfected, clasped by the sec- 
ond ring, the latter pushed back and loosened from the balance of the 
epiderm. Of the second ring the narrower posterior extension is quite 
empty ; its anterior chambers are closely filled with the tumid skin, 
the loss of the ring being prevented in this manner, while the outer 
swelling of the new button is crowding it backward. A considerable 
shrinkage of the skin takes place after the moult ; it is insufficient to 
allow the ring to slip off, though admitting of great freedom of motion. 
In front of the border of the second ring, Fig. 5, lies the fold, shrunken 
by alcohol in the specimen, by which the ring was displaced, and which 
was to become the largest chamber of the next succeeding. This fold is 
usually hidden by the epiderm attached to the ring, as in Fig. 6, until 
the operation of sloughing has been finished. The mass of bone oc- 
cupies the place of eight or more of the vertebre in this stage, the lines 
of separation being still noticeable to some extent. By a longitudinal 
section the cord and vessels are disclosed in their original positions, sur- 
rounded now by spongy bone, in which the cavities radiate from the 
centre toward the surfaces. On the upper and lower faces there is less 
indication of the composition. 
Figures 7 and 8 were taken from a large specimen of Crotalus hor- 
ridus, Linn. In it the traces of the vertebre in the terminal bone are 
almost obliterated ; the bone has thickened, pushed forward at the edges, 
and otherwise enlarged. Along with this there has been an excessive 
development of the muscles of the tail. The rattle is entire, of eleven 
rings and a button. The hinder seven of the rings belong to the period 
of the snake’s most rapid growth; they form the “tapering rattle” com- 
mon to the young individuals, formerly used in classification of the 
species by some authors. Four of the rings and the button pertain to 
a part of the creature’s life in which the gain in size was much less 
rapid; they form the “ parallelogramic rattle” of the same writers. 
The mistaken use of these features in specific diagnoses no doubt arose 
from study of incomplete rattles. The change from the taper to the 
more nearly parallelogramic takes place about the seventh ring, — in 
Sistrurus miliarius often with the sixth, with the larger species fre- 
quently with the eighth, —and affords the means of obtaining an ap- 
proximate idea of the comparative age of the owner of the series of 
rings. The figures show the rattle as commonly held by the snake 
when crawling. In a single series of rings there is much variation in 
