884 13. COLUBRIDAE 
occur within the area under consideration by the number of 
its gastrosteges and the position of the light nuchal collar. 
The gastrosteges are more numerous than in 7. nigriceps 
and T'.. planiceps but fewer than in T. eiseni. The collar 
does not involve the parietal plates in any of those species. 
Genus 44. Trimorphodon 
Trimorphodon Cope, Proc. Acad. Nat. Sci. Phila., 1861, p. 297 (type, 
T. lyrophanes); Cope, Report U. S. Nat. Mus. for 1898, 1900, 
p. 1101. 
The body is not much elongate, with tail of moderate 
length. The head is wide, more or less triangular, and very 
distinct from the slender neck. The snout is more or less 
truncate. The head plates are normal. The nasals are 
distinct. There are two loreals, one in front of the other. 
The preoculars and temporals are numerous. The scales 
are smooth, in 20 to 27 rows; often in an even number. 
Posterior maxillary tooth elongate, grooved; anterior teeth 
elongate; intermediate teeth shorter. The eye is large with 
vertically elliptic pupil. 
This genus includes a number of Mexican species, only 
one of which occurs within our geographic limits. 
204. Trimorphodon lyrophanes Cope 
Lyre SNAKE 
Lycodon lyrophanes Cope, Proc. Acad. Nat. Sci. Phila., 1860, p. 343 
(type locality, Cape St. Lucas, Lower California). 
Tr:morphodon lyrophanes Cope, Proc. Acad. Nat. Sci. Phila., 1861, 
p- 297; Core, Bull. U. S. Nat. Mus., No. 1, 1875, p. 38; Yarrow, 
Bull. U. S. Nat. Mus., No. 24, 1883, pp. 15, 98; Cope, Proc. Amer. 
Philos. Soc., 1886, p. 286; Cope, Bull. U. S. Nat. Mus., No. 32, 
1887, p. 68; Cope, Proc. U. S. Nat. Mus., Vol. XIV, 1892, p. 679; 
Van Densurcy, Proc. Cal. Acad. Sci., Ser. 2, Vol. 5, 1895, p. 1553 
Mocauarp, Nouv. Arch. Mus. Hist. Nat., Paris, Ser. 4, Vol. I, 
1899, p. 330; Core, Report U. S. Nat. Mus. for 1898, 19900, p. 1102; 
