Part 3

Preoculars

Of the 245 specimens examined, 242 (98.8%) have one preocular on each side. Both preoculars are absent from two specimens, and one specimen has 1-0. In each case when a preocular is lacking, the "preocular" and prefrontal are fused. One specimen having 1-1 preoculars has both of them reduced to small vertical slivers.

Postoculars

Of the 245 specimens examined, 242 (98.8%) have one postocular on each side. Postoculars are 2-1 in two specimens and 1-2 in one. In one specimen the lower of the two postoculars on each side is very small, being approximately 1/6 the diameter of the upper one (measured with an ocular micrometer).

Temporals

Of the 245 specimens examined, 235 (95.9%) have 1 + 1 temporals on each side. Four specimens exhibit addition of temporals: one specimen has two secondary temporals on the left, and one has a tertiary temporal on the left. Two specimens have partly healed head injuries that probably caused atypical temporal conditions: one specimen has two primary temporals on the left, and one has two secondary temporals on the left and two upper and one lower secondary temporal on the right.

Six specimens exhibit reduction of temporals: one lacks a primary temporal on the left ("temporal" is fused with sixth supralabial), two lack secondary temporals on the right, and three lack secondary temporals on the left. The right secondary "temporal" of one specimen is separated from the supralabials by a posterior extension of the primary temporal.

Of the 246 specimens examined, 200 (81.3%) have both primary temporals in contact with their adjacent postoculars. Thirteen specimens (5.3%) have only the left primary temporal in contact with the postocular and eight (3.3%) have only the right primary temporal in contact with the postocular. Twenty-five specimens (10.2%) have both primary temporals separated from the postoculars. Separation of the primary temporal from the postocular, whenever it occurs, results from contact of mutual extensions from the adjacent parietal and supralabial (usually the fifth).

Nasal

Of the 243 specimens examined, 237 (97.5%) have the nasal divided below the naris on both sides. Three specimens have the nasal completely divided (above and below the naris) on only the left side; one specimen has a completely divided nasal on only the right side. A groove, but not a complete division of the nasal, is present above the left naris of one specimen. One specimen lacks the typical division below the naris on both sides, but a complete suture is present posterior to the naris and the resulting postnasal scales are, according to position, loreals.

Contact of prefrontal with supralabials

Of the 243 specimens examined, 147 (60.5%) have the prefrontal separated from the labials on each side. Of the remaining 96 specimens, 53 (21.8% of the 243) have the prefrontals in contact with the second labial on each side; five other variations of this characteristic were observed (Table 2).

TABLE 2. Variation in Contact of the Prefrontals and the Labials in 243 Specimens of Tantilla gracilis.

----------------------------------------------------+---------+---------- |Number |Per cent CHARACTERISTIC |of |of |specimens|occurrence ----------------------------------------------------+---------+---------- No contact | 147 | 60.5 Contact of prefrontal with second labial on right | 26 | 10.7 Contact of prefrontal with second labial on left | 10 | 4.1 Contact of prefrontal with each second labial | 53 | 21.8 Contact of prefrontals with labial two on left and | | labial three on right | 1 | 0.4 Contact of prefrontals with labial three on left and| | labial two on right | 3 | 1.2 Contact of prefrontals with labial two on left and | | labials two and three on right | 3 | 1.2 ----------------------------------------------------+---------+----------

The specimen having the prefrontal in contact with labial 2 on the left and labial 3 on the right has seven supralabials on the right, the extra labial being added anterior to the eye. In two of the three specimens with the prefrontals in contact with labial 3 on the left and labial 2 on the right, the preoculars and prefrontals are fused on each side; the third specimen has each preocular reduced to a small vertical sliver. Of the three specimens having the prefrontals in contact with labial 2 on the left and labials 2 and 3 on the right, two are typical with respect to other characteristics that might result in this atypical condition, but one has the prefrontals and preoculars fused.

Supralabials entering orbit

Of the 246 specimens examined, 233 (94.7%) have the third and fourth supralabials entering each eye (Table 3). All snakes that have the fourth and fifth labials entering the orbit on either side also have seven supralabials on the same side. One specimen having only the fourth labial entering the eye on the right side also has six supralabials on that side, but the third supralabial is split diagonally and the part contacting the eye does not contact the lip and hence is not a supralabial. The remaining three atypical conditions (4/3 + 4; 3 + 4/3 + 4 + 5; 3 + 4 + 5/3 + 4) occur only one time each and on snakes having 6-6 supralabials.

Contact of mental with chin-shields

Of the 246 specimens examined, 190 (77.2%) have the mental in contact with both anterior chin-shields. The mental is in contact with only the left anterior chin-shield in 15 specimens, only the right anterior chin-shield in 2 specimens, and the mental does not contact either anterior chin-shield in 39 specimens. Separation of the mental and an anterior chin-shield always results from the posterior elongation of a first infralabial.

TABLE 3. Variation in Number of Supralabials Entering the Eye in 246 Specimens of Tantilla gracilis.

----------------------+-----------+------------ SUPRALABIALS | Number of | Per cent of ----------------------+ specimens | occurrence Left | Right | | ----------+-----------+-----------+------------ 3 + 4 | 3 + 4 | 233 | 94.7 4 + 5 | 3 + 4 | 4 | 1.6 4 | 3 + 4 | 1 | 0.4 3 + 4 | 4 + 5 | 5 | 2.0 3 + 4 | 4 | 1 | 0.4 3 + 4 | 3 + 4 + 5 | 1 | 0.4 3 + 4 + 5 | 3 + 4 | 1 | 0.4 ----------+-----------+-----------+------------

Dorsal scale rows

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)