Vol. II, Pt. I] VAN DENB URGH—SLEVIN—GALAPAGOAN LIZARDS 155 



Tropidurus bivittatus (Peters) 

 Chatham Island Lizard 



1843, Leiocephalus grayii, Bell, Zool. Beagle Rept, 1843, p. 24 (part) ; 

 Gray, Cat. Lizards, 1844, p. 218 (part) ; Gunther^ Proc. Zool. Soc. Lond., 

 1877, p. 67 (part). 



1871, Craniopeltis bivittata, Peters, Mon. Berlin. Acad., 1871, p. 645 

 (type locality Chatham Island, Galapagos Archipelago). 



1876. Tropidurus (Craniopeltis) grayii, Steindachner, Festschrift 

 Zool.-Bot. Ges. Wien, 1876, p. 310 (part). 



1885, Tropidurus grayi, Boulenger, Cat. Lizards, II, 1885, p. 172. 



1889, Tropidurus lemniscatus, Cope, Proc. U. S. Nat. Mus., XII, 1889, 

 p. 145 (type locality Chatham Island, Galapagos Archipelago); Baxjr, 

 Biol. Centralbl., X, 1890, pp. 478, 479. 



1891, Tropidurus bivittatus, Boulenger, Ann. and Mag. Nat. Mus., (6), 

 VII, 1891, p. 501; Baur, Festschrift fiir Leuckart, 1902, p. 272; Heller, 

 Proc. Washington Acad. Sci., V. 1903, p. 80. 



Diagnosis. — Neck with fewer folds, sides of neck covered 

 with scales instead of granules ; not more than 65 scales around 

 middle of body; males longitudinally striped; no red in 

 coloration; crest of males not very high. 



Types. — The material upon which Peters based his descrip- 

 tion of Craniopeltis bivittata was secured on Chatham Island 

 by Dr. Kingberg, in 1852, and probably is in the Museum of 

 Stockholm. Cope's Tropidurus lemniscatus was described 

 from specimens collected by the naturalists of the "Albatross," 

 in 1887-88, upon Chatham Island. These specimens are now 

 Nos. 14945 to 14964 of the U. S. National Museum collection. 



Distribution. — This species is restricted to Chatham Island, 

 Galapagos Archipelago. 



Material. — The Academy's collection contains about two 

 hundred and eighty specimens of this species, of which 

 seventy-three males and forty-two females have been included 

 in the table of scale counts. 



Description of adult male No. 9920. — The head is covered above with 

 smooth scales; interparietal largest, broader than long; five or six large 

 supraoculars; superciliaries imbricate; four superior and five inferior 

 labials, to below the middle of the eye; rostral very broad and low; 

 symphyseal broad, followed by a series of large sublabials, of which all 

 but the first are separated from the infralabials by a row of smaller 

 plates. Ear-opening large, with an anterior denticulation of five or six 

 narrow scales. Side of neck between ear-opening and fore limb with 

 few folds, covered with keeled, imbricate scales. Strong antehumeral, but 

 no complete gular, fold. A well-developed median dorsal crest begins a 

 short distance behind the interparietal, and runs continuously to and along 

 the tail, being highest on the proximal fourth of the tail. The dorsal 

 regions of the neck, body, and tail are covered with keeled, mucronate 

 scales, which, on the body, change gradually to smaller, keeled, mucro- 

 nate laterals. These again change gradually into the smooth ventrals, 

 which are much smaller than the dorsals. The gular scales are smooth, 



