178 : [OcrosER, 
Remarks. In Tropidinotus taxis pilotus the bars upon the back are much wider 
apart than in the above species, and it has but two posterior ocular plates; the 
arrangement of the temporal plates is also different; the frenal plate is much 
larger, and it has thirty-one rows of scales. Tropidonotus taxis pilotus is remark- 
able for its great size,being perhaps larger than any of our known water serpents; 
transversus is a much smaller animal. The markings upon the back and sides 
correspond in some degree with Say’s description of Coluber calligaster, but 
the scales in C. calligaster are smooth. The latter animal is most probably the 
one well known as Col. eximius. 
PHRYNOSOMA PLANICEPS. 
Sp. Char. Head,mere compressed, longer and broader than in P. cornutum ; 
nostrils within the supraciliary ridge; upper jaw bordered posteriorly by a row 
of pointed spines; central spine of the crown separated from the two adjacent 
spines by a wide interval; front part of head furrowed in the centre; scales of 
chin of nearly equal size; abdominal scales smooth or indistinctly carinated ; 
tail longer than in cornutum, and less suddenly tapering to a point; ground 
color of animal light yellow or ash color; (brown mingled with yellow i 
cornutum.) 
Dimensions. Length of head 9 lines; greatest vertical measurement 7 lines ; 
breadth posteriorly, including spines, 1 inch 2 lines; length of body to vent 
3 inches; length of tail 1 inch 7 lines; length of humerus 7 lines; of fore arm 
63; of hand to extremity of longest finger, including nail, 73 lines; length of 
thigh 9 lines; of tibia 9 lines; of foot to extremity of longest toe nail 94 lines ; 
total length 5 inches 4 lines. | 
Habitat. Western Texas, near the Rio Grande. 
SCELOPORUS MARMORATUS. 
Sp. Char. Four plates behind the rostral and between the nostrils, the two 
first more or less linear; six plates upon the frontal region; behind these, five 
plates surrounding one which is pentagonal ; posterior to these, midway between 
the supraciliary ridges, a single large hexagonal plate (intraorbital;) snout 
rather pointed, more narrow than in delicatissimus ; body slender; scales bi- 
punctate posteriorly. . 
Dimensions. Length of head 64 lines; greatest breadth 4 lines; length of 
neck and body to vent 1 inch 5 lines; length of tail 2 inches 102 lines; length 
of humerus 3 lines; of fore arm 3 lines; length of hand to extremity of longest 
finger 4 lines; length of thigh 5 lines; of tibia 5 lines; of foot to extremity of 
ee toe 7 lines; circumference of body 14 lines; total length 4 inches 10 
ines. 
Habitat. San Antonio, Texas. 
\ 
ScELOPORUS: DELICATISSIMUS. 
Sp. Char. Four plates behind the rostral and between the nostrils; the two 
first much smaller than the latter; nine plates upon the frontal region, in two 
rows (four in front and five posteriorly;) behind these five plates without the 
central pentagonal one above described; snout somewhat obtuse; body more 
slender than that of marmoratus; scales bipunctate posteriorly. 
Dimensions. Length of head 6 lines ; greatest breadth 4 lines; length of neck 
and body to vent 1 inch 5 lines; length of tail 3 inches 2 lines; length of hu- 
merus 3 lines; of fore arm 3 lines; of hand to extremity of longest finger 4 
lines ; of thigh 4 lines; of tibia 5 lines; of foot to extremity of longest toe ~ 
72 lines; total length 5 inches 1 line. 
Habitat. San Antonio, Texas. 
PSAMMOPHIS FLAVI-GULARIS« 
Sp. Char. Head long, superior and inferior marginal outline of cranial portion 
slightly convex; temples depressed; body robust; color light brown or fuscous 
above ; chin, throat, abdomen, and under part of tail yellow; 17 rows of scales ; 
abdominal scuta 190; sub caudal 97. 
