[Illustration: FIG. 2. Number of ventrals in females and males of _T.
gracilis_.]
Females have from 122 to 137 (mean, 130.8 +- 0.26; N = 107) ventrals;
males have from 117 to 131 (mean, 122.3 +- 0.21; N = 139; Fig. 2). Of the
246 specimens examined, 29 (11.8%; 11 females and 18 males) have an
added half-ventral immediately anterior to the anal plate. Of these
specimens, 27 have the added half-ventral on the left side and two have
it on the right. Five specimens have the last ventral divided similar to
the normal division of the anal plate. One specimen has the last ventral
incompletely divided transversely. Excluding the last ventral, seven
specimens have divided ventrals (half-ventrals). Four of these specimens
have added half-ventrals on the right side (two specimens with one
half-ventral each, one specimen with two half-ventrals, and one specimen
with three half-ventrals), and four have added half-ventrals on the left
side (one half-ventral on each specimen).