164 BULLETIN : MUSEUM OF COMPAKATIVE ZOOLOGY. 



Habitat. — Cocos Island, Pacific Ocean, off Costa Eica, Central America. 



Type. — v. S. National Museum, No. 22106; Feb, 28, 1891; collector, 

 Charles H. Townsend. 



Description. — ^ 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 subcylindric, scales about the size of ventrals, keeled, with 

 hardly an indication of verticels ; body compressed ; adpressed hind limb 

 reaches beyond 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 iiregular 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. 



Total length 123 mm. 



Snout to ear-opening 13 " 



Snout to vent 47 " 



Tail from vent 76 " 



Fnre limb 22 " 



Hind limb 37 " 



Tibia 12 " 



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. 



