Part 2

The number of rows of dorsal scales was determined at five locations: a) around the neck--counts were made from each side diagonally and posteriorly from the anteriormost dorsal scale in contact with the first ventral (see below)--counts from the left and right sides are the first and second counts, respectively, recorded in the scale formula; b) one head length posterior to head--counts were made either diagonally and posteriorly or in a zig-zag pattern, beginning at the end of the second count around the neck--this is the third count recorded in the scale formula; c) midbody (approximated)--counts were made either diagonally and posteriorly or in a zig-zag pattern--this is the fourth count in the scale formula; d) anterior to anus (preanal)--counts were made in a zig-zag pattern beginning on one side and ending on the other at the first dorsal scale in contact with the anal plate--this is the fifth count in the scale formula.

We followed the method of Dowling (1951:98-99) in counting ventrals, and the anal plate was determined as entire, divided, or partly divided. Subcaudals were counted on only the right side beginning at the first scale that contacts a corresponding scale from the opposite side; fusion of particular pairs of subcaudals was determined. The "spine" at the tip of the tail was not counted. The head scutellation of each specimen was examined for abnormalities.

We determined the number of fangs and the number of maxillary teeth anterior to them and recorded the presence or absence of a diastema between the anterior fang and the maxillary tooth immediately preceding it. The diastema, if present, is a space distinctly wider than the spaces separating the prediastemal teeth.

The point of intersection of two perpendicular lines of an ocular grid determined which tooth-socket occurs directly opposite the distal tip of the suborbital process (Fig. 5b), but if that point occurs between two sockets then the number recorded was the number of the tooth immediately anterior to that point plus one-half.

The anterior and posterior edges of the suborbital process were determined as parallel or not at any point by aligning them with parallel lines on an ocular grid (Fig. 5b).

The angle of the posterior edge of the lateral flange was determined as an acute, obtuse, or right angle by fitting it to a pair of perpendicular lines of an ocular grid (Fig. 5b).

The number of lateral anterior foramina (Fig. 4b) was determined. If only two are present, their lengths (anterior to posterior) were compared by measuring them with an ocular micrometer. Also, if two lateral anterior foramina are present, the point of intersection of two perpendicular lines of an ocular grid determined which tooth-socket occurs directly below the center of the posterior foramen (Fig. 4b).

RESULTS

General Characteristics

From the data given by Force (1935), Taylor (1936), and Kirn et al. (1949), and from our own data, we conclude that a typical specimen of gracilis, meaning a specimen having the usual characteristics of the species, has the following characteristics in combination: supralabials 6-6; infralabials 6-6; preoculars 1-1; postoculars 1-1; temporals 1 + 1 on each side; nasal divided below naris; supralabials 3 + 4 entering orbit; mental in contact with chin-shields; all five dorsal scale counts 15; and plate divided. (In the present work we use the words usual, unusual, typical, and atypical with neither quotation marks nor apology).

Of the 244 specimens on which we could examine each of these characteristics, only 125 (51.2%) have all of the typical characteristics in combination. The 119 specimens that do not possess all of the typical characteristics in combination include 31 (12.7% of the 244) that lack at least two of the typical characteristics.

Sex

The sample (N = 246) is composed of 107 (43.5%) females and 139 (56.5%) males.

Measurements

Females have total lengths from 96 to 244 mm. (mean, 173.3; N = 79). One female (KU 83480) measuring 244 mm. may be the longest specimen known (Conant, 1958, reports the longest as 9-1/8 inches--approximately 232 mm.). Males have total lengths from 96 to 215 mm. (mean, 162.4; N = 109). Females have tail lengths from 16 to 50 mm. (mean, 34.6; N = 79), and males have tail lengths from 21 to 53 mm. (mean, 37.8; N = 109).

The ratio of tail length to total length in females is from 0.17 to 0.22 (mean, 0.20; N = 79); in males it is from 0.21 to 0.27 (mean, 0.23; N = 109; Fig. 1). Juveniles (those less than 125 mm. in total length according to Force, 1935: tables 1 and 2) have proportionally shorter tails than do adults; the ratio of tail length divided by total length is 0.17-0.21 (mean, 0.18; N = 14) in females and 0.21-0.23 (mean, 0.22; N = 16) in males. Adult females (125 mm. or more in total length) have ratios from 0.18 to 0.22 (mean, 0.20; N = 65) and adult males have ratios from 0.21 to 0.27 (mean, 0.23; N = 93).

Of the 246 specimens examined, 58 have incomplete tails. Of these 58 specimens, six had freshly broken tails, so we assume that 52 (21.1% of the 246) have incomplete tails resulting from natural causes; the remaining six specimens could have had their tails broken at or soon after capture, assuming that none of the snakes was retained in captivity for an extended period.

Supralabials

The supralabials are either six (usually) or seven on a side (Table 1). When seven supralabials are present on either one or both sides, the addition results from one of the following conditions: a) 5 is divided to form 5 and 6 (N = 6); b) 2 and 3 form 2, 3, and 4 (N = 1); c) 5 and 6 form 5, 6, and 7 (N = 12); d) 4, 5, and 6 form 4, 5, 6, and 7 (N = 1); e) 1 and 2 form 1, 2, and 3 (N = 1); f) 1, 2, and 3 form 1, 2, 3, and 4 (N = 1); g) 2 is fused with the nasal, and 3 and 4 are reduced to granules (N = 1); h) type of addition unknown (N = 5).

TABLE 1. Variation in Number of Supralabials (N = 245) and Infralabials (N = 246) of Tantilla gracilis.

------------+----------+-----------+------------+---------+---------- Number |Number |Per cent |Number |Number |Per cent of |of |of |of |of |of Supralabials|specimens |occurrence |infralabials|specimens|occurrence ------------+----------+-----------+------------+---------+---------- 6-6 | 221 | 90.2 | 5-5 | 5 | 2.0 6-7 | 10 | 4.1 | 5-6 | 4 | 1.6 7-6 | 10 | 4.1 | 6-5 | 5 | 2.0 7-7 | 4 | 1.6 | 6-6 | 229 | 93.1 | | | 6-7 | 1 | 0.4 | | | 7-6 | 2 | 0.8 ------------+----------+-----------+------------+---------+----------

In three of the four specimens with 7-7 supralabials, the type of addition is the same on each side, whereas the other specimen has a different type of addition on each side. Of the 23 examples for which the type of addition is known, 19 (82.6%) have the increase in number on the posterior half of the series.

In one specimen the third supralabial on the right is diagonally divided and the resulting upper part does not contact the edge of the lip; hence the specimen has 6-6 supralabials.

Infralabials

The infralabials are five, six (usually), or seven on a side (Table 1). When five infralabials are present on either one or both sides, the reduction results from one of the following conditions: a) 2 and 3 are fused (N = 3); b) 1, 2, and 3 form 1 and 2 (N = 6); c) 2, 3, and 4 form 2 and 3 (N = 3); d) 5 is separated from the edge of the lip by a projection from an adjacent infralabial (N = 1); e) 1, 2, 3, and 4 form 1, 2, and 3 (N = 2); f) type of reduction unknown (N = 4).

Of the specimens with 5-5 infralabials, two have the same type of reduction on each side, one has a different type of reduction on each side, and the type of reduction is unknown for the other two specimens.

When seven infralabials are present on either one or both sides, the addition can result from infralabials 2 and 3 forming 2, 3, and 4 (N = 2); the type of addition is unknown in one specimen.

In one specimen the second infralabial on the right side is reduced to a small wedge-shaped granule and in another specimen several infralabials on both sides are irregularly divided horizontally, although both specimens have six infralabials on the sides having the abnormalities.