54 



COXtTBEID^. 



Scales in 21 rows ; ventrals 236 ; subcaudals 

 70 ; head with a lyre-shaped pattern ; 

 dorsal spots in pairs 3. lyrophanes, p. 56, 



II. Six or seven upper labials ; scales in 23 rows. 



4. tan, p. 56. 



1. Trimorphodon biscutatus. 



Dipas hiscutata, Dum. ^ Bibr. vii. p. 1153 (1854). 



Dipsadomorphus biscutatus, Oiinth. Cat. p. 176 (1858). 



Trimorphodon biscutatus, Cope, Proc. Ac. Philad. 1861, p. 297, and 

 Proe. Amer. Philos. Soc. xi. 1869, p. 152 ; Dugis, La Naturaleza, 

 vi. 1882, p. 145, fig. ; Cope, Proc. Amer. Philos. Soc. 3xiii. 1886^ 

 p. 286 ; (iunfh. Biol. C.-Amer., Sept. p. 174 (1895). 



Eteirodipsas biscutata, Jan, JElenco, p. 105 (1863). 



Trimorphodon major, Cope, Proc. Amer. Philos. Soc. xi. 1869, p. 153. 



Sibou biscutatum, part., Garm. N. Amer. Pept. p. 16 (1883). 



? Trimorphodon lambda, Cope, Proc. Amer. Philos. Soc. xxiii. 1886,. 

 p. 286. 



Eostral broader than deep, the portion visible from above measur-- 

 ing one fourth to one half its distance from the frontal ; internasala 

 much shorter than the praefrontals, which are usually broader than 

 long ; frontal once and one fourth to once and a half as "long as- 

 broad, as long as or a little longer than its distance from the end of 

 the snout, as long as or slightly shorter than the parietals ; two or' 

 three loreals, rarely one ; two (rarely one) preeooulars, usually with- 

 a subocular below ; the upper pr^ooular in contact with or narrowly 

 separated from the frontal ; three postoculars ; temporals small, 

 scale-like, 2+3, 3+3, or 3+4; nine (rarely eight) upper labials, 

 fourth and fifth (in one specimen third, fourth, and fifth, owing 

 to the absence of subocular) entering the eye ; four or five lower 

 labials in contact with the anterior chin-shields, which are longer 

 than the posterior. Scales in 23 to 27 rows, usually 25. Ventrals 

 234-264 ; anal divided ; subcaudals 74-94. Pale greyish or 

 brownish above, with dark, black-edged cross-bars or transverse 

 markings with light centre ; head with angular dark bands sepa- 

 rated by a crescentic transverse light area between the eyes and a, 

 A- or A-shaped one on the occiput ; lower parts whitish, more or 

 less mottled with brown, with large dark brown spots on the sides. 



Total length 1200 miUim. ; tail 230. 



Mexico to Panama. 



a. $ (Sc. 25 ; V. 251 ; Mazatlan. Hr. A. Forrer TO 1 



0.78). '- -' 



b-d, e-g. S (Sc. 25, 25, Presidio. Hr. A. Forrer fCL 



24; V. 250, 249, 243; '" "' 



0. 85, 84, 87), $ (Sc. 



25; V.255;C.78),& 



yg. (Sc. 25, 23; V. 



244,237; 0.86,86). 

 h. Hgr. $ (Sc. 25 ; V. Oaxaca. M, Sall^ [0.1. 



253; 0.74). '- -' 



