SYNOPSES AND DESCRIPTIONS. 79 
XENODON. 
Boie, 1827, 
Stout, subeylindrical, belly flat; head distinct from the neck, short, 
broad, crown flat; tail short, stout, tapering. Posterior maxillary teeth 
larger, smooth, Eye large. Crown-shields nine. <A loreal. Rostral 
moderate, reaching the top of the snout. Nasal divided. Scales smooth, 
in oblique series, much imbricate, Anal entire or divided. Subcaudals in 
two rows. Brazil to Mexico; East Indies. 
XENODON BERTHOLDI. 
Jan, 1863, Arch. per la Zool. IT, fasc. IT, 108. 
Stout, belly broad; head large, broad, crown flattened; tail short, taper- 
ing. Eye moderate, pupil round. Posterior maxillary tooth long, smooth. 
Crown-shields nine, short, broad. Prefrontals bent down to the loreal. 
Frontal broad, concave or truncate in front. Parietals as broad as long. 
Nasal in two parts, nostril between. Loreal small. One anteocular, short, 
high. Postoculars two or three, varying much in size and shape in differ- 
ent individuals. A large temporal in contact with the oculars. Labials 
eight, fourth and fifth in orbit, seventh largest. Infralabials eleven, sixth 
largest. Submentals two pairs, anterior larger. Scales smooth, lustrous, 
in 19 rows, lateral very oblique, much imbricate. Ventrals 149. Anal 
entire. Subcaudals 47 pairs (42—47). 
Brownish, with twelve to fourteen dark light-edged transverse bands, 
which widen and bifurcate on the flanks, thus inclosing on the middle of 
the back a light space, somewhat of a lozenge-shape, which frequently has 
a darker patch in its center. Lower part of flank spotted with dark. 
Abdomen yellowish to olive, mottled with darker. This species resembles 
X. rhabdocephalus very much; the most prominent difference is in the entire 
anal shield. Closely allied to X. colubérinus Gthr. Mexico. 
TLYPSIGLENA. 
Cope, 1860, Pr. Ac. N. Se., Phil., 246. 
Cylindrical; head distinct from the neck, depressed, broad posteriorly, 
conic anteriorly; tail short, less than one fourth of the total. Upper poste- 
rior maxillary tooth longer, smooth, separated by an interspace. Pupil 
elliptic, erect. Crown-shields normal. Nasal divided. A loreal. Ocu- 
lars 2—2. Seales smooth. Anal bifid. Subcaudals in two rows. <Ari- 
zona; Lower California, 
