Of the 245 specimens examined for this characteristic, 228 (92.7%) have
scale counts of 15-15-15-15-15. The number of scale rows around the neck
and one head length behind the head are 15 except in a single specimen
that has 14 scale rows at these three places. The number of scale rows
around midbody is 15 in 244 of 246 specimens (99.2%); two specimens have
14 scale rows around midbody. The number of preanal scale rows is more
variable; counts of 14 through 17 were recorded. Fourteen specimens have
14 preanal scale rows (5.7%), 229 have 15 preanal rows (93.1%), two have
16 preanal rows (0.8%), and one has 17 preanal rows (0.4%). Known causes
for atypical numbers of preanal scale rows are listed in Table 4. A
preanal count at one head length anterior to the anus would have omitted
most of the above variation in numbers of preanal scale rows.
TABLE 4. Atypical Numbers of Preanal Scale Rows in Specimens of Tantilla
gracilis.
-------+---------+--------------------------------------------+----------
Preanal|Number | |Per cent
scales |of | CAUSE |of
|specimens| |occurrence
-------+---------+--------------------------------------------+----------
| |Scale rows seven and eight on left fuse |
14 | 10 |within the last five ventrals | 4.1
| | |
| |Scale row two on the right is lost adjacent |
14 | 1 |to the penultimate ventral | 0.4
| | |
| |Scale row eight on the left divides adjacent|
16 | 1 |to the last ventral | 0.4
| | |
| |A scale row is added on the right adjacent |
16 | 1 |to and anterior to the anal plate | 0.4
| | |
| |A scale row is added on each side adjacent |
17 | 1 |to and anterior to the anal plate | 0.4
-------+---------+--------------------------------------------+----------
The complete dorsal scale formula for KU 83620, a male, is as follows:
6 + 7(2) + 7(4) 6 + 7(11)
15 --------- 13 --------- 14 --------- 15 ---------- 13 --------------,
6 + 7(2) +7(5) 6 + 7(11) 6 = 6 + 7(17)
14 ------------- 13---------,
6 + 7(18) +7(25)
+ 7(26) 6 + 7(38) +7(39)
14 ---------- 15 ---------- 14 ------------ 13---------- 14----------,
6 + 7(36) +7(42)
15 --------- 14 ---------,
-6(45) +7(53)
7 + 8(67) + 7(69)
15 ------------ 14 ----------- 15 ----------- 14 ---------- 15----------,
6 + 7(90) +7(93) 6 + 7(99)
14 ------------ 15(122).
+ 7(100)
Specimen 83620 is the only one for which we have determined the complete
dorsal scale formula. Obviously the formula is complex, and possibly the
specimen is atypical in this regard. Nevertheless, addition and
reduction of scale rows is apparent on other specimens and can be easily
observed by examining specimens under a dissection microscope.