164 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Habitat. — Cocos Island, Pacific Ocean, off Costa Rica, Central America. 
Type. —U. S. National Museum, No. 22106; Feb. 28, 1891; collector, 
Charles H. Townsend. 
Description. — g ad. U.S. Nat. Mus. No. 22106. Head twice as long as 
broad, longer than tibia; forehead slightly concave; frontal ridges nearly 
obsolete; upper head scales small, keeled ; scales of supraorbital semicircles 
moderately enlarged, separated by three scales; enlarged supraorbitals numer- 
ous, elongated, sharply keeled, in contact with semicirculars ; occipital shield 
elongate oblong, somewhat larger than ear-opening, separated from semicircu- 
lars by two scales; canthus rostralis very distinct, of six scales, the anterior 
ones small, the posterior two very long and narrow continued backwards in 
line with three superciliaries, which are also unusually long, narrow, and 
keeled ; posterior half of superciliary ridge granular ; a series of enlarged sub- 
oculars, keeled, not reaching lip ; loreal rows, about six, keeled ; eight supra- 
labials to below centre of eye, rugose ; ear-opening moderate, vertically oval ; 
dewlap moderate with a thickened edge of densely set short thick scales, those 
on sides of appendage distant and very elongate; gular scales small, long, and 
narrow ; dorsal scales much smaller than ventrals, and indistinctly larger than 
those on the flanks, and gradually but slightly increasing in size toward the 
vertebral line, where a few rows are distinctly keeled; no dorsal or cervical 
fold or crest; ventral scales larger, imbricate, keeled, like all the scales of the 
underside ; scales on anterior surfaces of limbs somewhat larger than ventrals, 
keeled ; tail subeylindric, scales about the size of ventrals, keeled, with 
hardly an indication of verticels; body compressed ; adpressed hind limb 
reaches heyond eye ; no enlarged post-anal scales. Color above dull brownish 
gray, irregularly and indistinctly mottled with dusky which shows a tendency 
to form cross-bars on the tail; limbs more brownish with lighter roundish 
spots ; lores, temples, and sides of neck anteriorly with irregular white mark- 
ings ; a very distinct white, black-edged lateral band from sides of neck over 
the shoulder to groin; underside whitish ; throat with indistinct, brownish 
mottlings. 
DIMENSIONS. 
AN selg G5 b 610 905 @ oo o We ra, 
Snout toiear-opening» =... -gueu een Loni 
Snoutstosvient: < sch cos col n)e Omer Rein ne a 
Tailtromevent,: 10h) Qe ie Soeeiee ee. eee OMe 
Rorelimb: “(scene ee ee kena oe 
indatimibt “3 shee ee ee eee eee) re Coes 
AOE: ered Ra mRNA ELS) is edt ee ee TIARA 
Variation. — A slightly smaller female (U. S. Nat. Mus. No. 22107) differs 
chiefly in the absence of a dewlap and in coloration ; the white lateral band is 
present, but it is not edged with blackish, and there is in addition a narrow 
white vertebral band from occiput to root of tail. 
