Maxillary teeth anterior to fangs 10-14 (mean, 12.1; N = 20); tooth-socket number 6.5-8.5 (mean, 7.2; N = 20) directly opposite distal tip of suborbital process; lateral anterior foramina 1-3 (mean, 1.8; N = 20); tooth number 6-9 (mean, 6.9; N = 12) directly below center of posterior foramen (if only two foramina present). Three specimens lack a diastema and 17 specimens have a diastema. The anterior and posterior edges of the suborbital process are parallel in two specimens and not parallel in 14; the process is broken in four specimens. The lengths (anterior to posterior) of the lateral anterior foramina (if only two are present) are approximately equal in six specimens, and in six the anteriormost one is the longest; six specimens have one foramen and two specimens have three foramina. All specimens examined have two fangs, with the posterior edge of the lateral flange forming an obtuse angle. [Illustration: FIG. 4. Lateral view of right maxilla of _T. gracilis_ (KU 83484), × 39. Actual length of bone is 2.44 mm. A. Detail of bone. B. Outline sketch of bone to illustrate characteristics examined. Lateral anterior foramina (LF); fangs (F); "prediastemal" maxillary teeth (MT); lateral flange (PLF); perpendicular lines, A-B and C-D, are used to determine which tooth-socket occurs directly below the center of the posterior foramen (the specimen illustrated is atypical because there are three foramina present).] Discussion and Conclusions Generic characteristics of _Tantilla_ are as follows: size small, body slender, head not noticeably distinct from body; preoculars one; postoculars one or two; nasals two; loreal absent; smooth dorsal scales in 15 rows; anal plate usually divided but sometimes single; subcaudals paired; usually two enlarged, posterior, grooved fangs on the maxilla separated by a small diastema from the other maxillary teeth (Baird and Girard, 1853:131; Cope, 1900:1110; Dunn, 1928:24; Blanchard, 1938:369; Schmidt and Davis, 1941:268; Wright and Wright, 1957:722; Conant, 1958:180). Of these characteristics, only the following were invariable in our sample: size small, body slender, head not noticeably distinct from body; postoculars one or two; smooth dorsal scales; posterior grooved fangs on maxilla. The dorsal scales, anal, and subcaudals were "correct" 92 per cent of the time; the preoculars and nasals were "correct" 97 per cent of the time. [Illustration: FIG. 5. Ventral view of right maxilla of _T. gracilis_ (KU 83484), × 39. Actual length of bone is 2.44 mm. A. Detail of bone. B. Outline sketch of bone to illustrate characteristics examined. Lateral flange (PLF) forms an obtuse angle (ADC) with main axis of bone (AB); a reference line (2), perpendicular to the main axis of the bone, is used to locate the tooth-socket directly opposite the tip of the suborbital process (SOP); the anterior and posterior edges of the suborbital process are not parallel at any point (reference lines 1 and 3).]