66 
region of the distribution. There is a wide range in the 
maximum number of scale rows around the anterior part of 
the body. The normal is 21; it may be increased to 23 and to 
25, or it may be decreased to 19 rows. We have been taught 
by Doctor Ruthven that for the purpose of comparing one set 
of observations with another the scale rows must be given 
permanent numbers, also, that it is necessary to select a speci- 
men having the maximum number of rows for the species. In 
this case it is one with 25 rows, and these are numbered I to 
XI, counting from the outer row inward to the median. In 
all specimens the maximum count is on the anterior part of the 
body and diminishes posteriorly. This decrease is due to the 
loss of definite scale rows, exactly as Doctor Ruthven has 
shown occurs in the genus Thamnophis (Fitzinger) 1843. 
In Ancistrodon halys, the sequence of suppression is as 
follows: 
rows, V row suppressed, leaving— 
Vil 
5 
3 
21 ae IV 
9 
7 , Which are continued to the vent 
rer 
The normal squamation is where there are 25 rows an- 
teriorly with the V row suppressed leaving 23 rows; next 
the VI row is suppressed leaving 21 rows; then the IV row is 
suppressed leaving 19 rows; finally the VII row is suppressed, 
leaving 17 rows which are continued without further loss to 
the base of the tail. The scale formula for this type would 
be written: 
25-23-21-19-17 (-V-VI-IV-VII). 
In a normal specimen the number of scale rows, the sequence 
of suppression, and the gastrostege level on the right and left 
sides of the body at which the rows terminate, may be thus 
expressed : 
MUSEUINE eiceieiccrrcieiie Locality Sex. G. 25-V. 23-VI. 21-IV. 19-VII. 17-Cont. 
U.S. N. M. 34024.... Yokohama ie id 748 14 14 101 103 136 130 
In specimens with the same number of scale rows there 
is a difference in the distance to which the suppressed rows 
extend down the body. From this have resulted the different 
accounts that are found in literature of the number of scale 
rows around the body. There are records of specimens with 
25, 23, 21, and 19 rows. It is evident that a specimen with 
25 rows anteriorly, and the V row continuing down the body 
to the level of the 80th gastrostege would be recorded as 
