SYNOPSES AND DESCRIPTIONS. 9 
contact with the labials. Labials about 20, infralabials 20 to 22. Scales 
in 65 to 69 rows, outer broader. Ventrals 233 to 240; subcaudals 52 
to 57. Brownish, varying from light to dark (in alcohol), with a dorsal 
series of quadrangular brown spots, emarginate anteriorly and posteriorly, 
separated from the series of triangular brown spots on the upper portion 
of the flank by an interrupted narrow line of light color, which is most 
distinct opposite the spots. Upper spots of the flank larger and more 
distinct. An irregularly placed series on the outer rows of scales and the 
edge of the abdomen. Spots darkening toward the tail, often with lighter 
centers. A brown line on the head from the frontal region to the neck. 
A brown line from behind the angle of the mouth through the eye to the 
loreal region, spreading toward its extremities. A bar from the eye to the 
lip. A pair of spots on each side of the lower jaw. Rostral with a spot. 
Seales irregularly punctulate or spotted. Mex. 
I have little doubt that this will eventually be degraded to the rank of a 
variety. Specimens at hand from the Isthmus of Darien are intermediates 
between this species and B. constrictor. 
Boa CONSTRICTOR. 
Var. isthmica. 
Body stout, compressed; head distinct; snout broad, truncate; tail short, 
prehensile. Rostral large, broader near the upper edge, concave at the 
sides and below, rounded above, surrounded by scales larger than the 
others of the head. Nasal divided. Eye surrounded by eighteen or nine- . 
teen scales. Several larger scales in front of the oculars. Two rows 
between oculars and labials. Labials 22-23. Infralabials 25-27. Scales 
small, flat, smooth, in 78 rows, outer broader. Ventrals narrow, 246. Sub- 
caudals 57, 
Ground color light greyish (in alcohol). Pattern of markings as in B.. 
constrictor. Transverse brown bands of the back twenty-five, posteriorly 
united by the darker margins with the triangular spot on the upper part 
of the flank. Beneath the latter on the flank there is a series of oblong, 
rounded spots, each enclosing a rounded spot of lighter color. A series of 
more or less broken quadrangular black spots on each side of the belly 
includes scales of the outer row. The spots unite on the tail so as to form 
a dorsal and subeaudal row. <A light brown band from rostral to neck 
includes several light spots on the occipital region. A brown band with 
