13 
DESCRIPTION OF A NEW SNAKE (OPISTHOTROPIS 
SPENCERI) FROM SIAM. 
By Matcotm A. SMITH, F.Z.S. 
WITH A PLATE. 
Diagnosis. Scales in 17 rows, nasals separated by the inter- 
nasals, praefrontal single, loreal in contact with the internasal, 7 
supralabials, 4th and 5th touching the eye. Nearest to O. maawelli 
Boulenger, from South Fokien, China, and 0. atra Gunther, said to be 
from West Africa, from both of which it differs in a number of small 
points. 
Description. Snout broadly rounded, much depressed ; nasal 
almost completely divided by a cleft running from the internasal to the 
1st labial ; rostral nearly twice as broad as deep, well visible above ; 
internasals subtriangular, about as broad as long; praefrontal single, 
large, two and a half times as broad as long ; frontal large, slightly 
longer than broad, as long as its distance to the rostral, nearly four 
times as broad as the supraocular ; loreal a little longer than deep, in 
contact with the internasal ; one prae- and and two postoculars ; tem- 
porals 142 or 24+2; seven supralabials, 4th and 5th touching the eye ; 
five infralabials in contact with the chin-shields, the anterior pair of 
which are larger than the posterior. 
Seales in 17 rows throughout, entirely smooth. Ventral: 183, 
anal divided, subcaudals 33 (?). 
Colour. Olive above, pale yellowish beneath, the colours ming- 
led on the three outer rows of scales. 
Total length, 600 mm. ; tail (imperfect) 72. 
Dentition. Maxillary, 25; palatine, 14; pterygoid, 18; man- 
dibular, 22. 
Type. Female; author's number, 1178, M. A. S., collected 
September, 1917, in Muang Ngow, N. Siam. 
This new species is described from a single specimen, which 
was obtained ina hill stream at about 300 metres elevation by Mr. 
F. D. Spencer, after whom I have much pleasure in naming it. 
The type will be presented to the British Museum of Natural 
History, London. 
I am indebted to Mr. C. L. Groundwater for the drawing of 
the head. 
VOL, III, NO, I, 1918, 
