174 « OPHIDIA. 
TRIMORPHODON. 
Dipsadomorphus, sp., Fitz. Syst. Rept. p. 27 ; Giinth. Cat. Col. Sn. p. 174. 
Trimorphodon, Cope, Proc. Ac. N. Sc. Phil. (1861) 1862, p. 297. 
Upon a material consisting of fourteen Mexican specimens, Mr. Cope established, 
beside the Dumerilian Dipsas biscuta’us, and the extralimital Lycodon lyrophanes 
from California, five other species as follows :— 
Trimorphodon tau, Cope, Proc. Am. Phil. Soc. 1869, p. 152, from ‘Tehuantepec. 
Trimorphodon upsilon, Cope, Proc. Am. Phil. Soc. 1869, p. 152, from Chibuahua, 
Guanajuato, Zacualtipan, and Guadalajara. 
Trimorphodon collaris, Cope, Journ. Ac. Nat. Sc. Phil. viii, p. 131 (1875), from 
Orizaba. 
Trimorphodon wilkinsonti, Cope, Proc. Am. Phil. Soc. 1886, p. 285, from Chi- 
huahua. | 
Trimorphodon lambda, Cope, Proc. Am, Phil. Soc. 1886, p. 286, from Guaymas. 
Mr. Cope has given several synopses of these species (the most recent in Proc. Am. 
Phil. Soc. 1886, p. 286) showing the characters by which he has arranged his specimens, 
and which I have attempted to apply to the material before me (sixteen specimens). 
However, I have found these characters to break down completely, so that scarcely 
one of my specimens would correspond with any of Mr. Cope’s descriptions, and the 
majority would have had to be described under new names. Therefore I am rather 
‘nclined to think that these snakes are subject to much individual variation in scales, 
scutellation, and colours. The latter, especially, change with growth. 
Among our sixteen specimens I distinguish, beside T. biscutatus, only one other 
form, for which I retain one of the Copean names—TZ. upsilon—as the one which has 
been used by Cope for specimens from various localities. 
1. Trimorphodon biscutatus. 
Dipsas biscutata, Dum. & Bibr. Erpét. vii. p. 1153. | 
Dipsadomorphus biscutatus, Giinth. Cat. Col. Sn. p. 176 ; Salv. P. Z. 8S. 1860, p. 457; 1861, p. 228. 
Dipsas biscutata, var. latifascia, Peters, MB. Ak. Wiss. Berl. 1869, p. 877. 
Trimorphodon biscutatus, Cope, Proc. Am. Phil. Soc. 1886, p. 286. 
Trimorphodon major, Cope, Proc. Am. Phil.-Soc. 1869, p. 163 ; Sumichrast, Bibl. Univers. 1873, 
p. 253. 
? Trimorphodon lambda, Cope, Proc. Am. Phil. Soc. 1886, p. 286. 
Hab. Mexico, Presidio, Mazatlan (Forrer), Colima (Xantus), Puebla (Peters), Guada- 
lajara (Cope), Oaxaca (Sallé), Tehuantepec (Sumichrast); GUATEMALA, Lanquin 
(Salvin) ; Nicaragua (Dow); Panama (Dow). 
More or less regular concentric brown chevron-bands across the head and neck. 
Scales in 24-27 series. Upper labials generally nine. 
