462 Bulletin American Museum of Natural History [Vol XLI 



of largest equal to 9 dorsal scales, often exceeded by tallest spines of dorsal crest; 

 width of the widest whorl (2 rows dorsally) very much less than distance from nostril 

 to anterior orbit; base of 5th to end of 4th toe equal to distance from anterior border 

 of ear to end of muzzle. Color light yellowish; black or intensely dark brown on 

 gular region and fold, breast and thoracic region to the line of the wrists (when arms 

 adpressed), also axilla and lateral area as high as the dorsolateral line; a short lenti- 

 cular black spot crosses the back between the points of insertion of the arms (its 

 middle corresponding with line of axillas), connected at its narrowed ends with some- 

 what irregular, longidutinal lines of black which, with the lenticular spot, mark out a 

 rectangle containing a central black spot, while a smaller black spot anteriorly on the 

 spines of the crest indicates the middle of the anterior boundary of the rectangle; 

 also a straight band of black crosses the back on a line with the elbows, curving 

 abruptly at the sides to join the black below the dorsolateral line. 



Measurements of the Type. — Total length, 668 mm.; tip of muzzle to anus, 

 286; tail, 382; tip of muzzle to fold, 102; tip of muzzle to posterior border of ear, 71 ; 

 head width, 60; hind leg, 170; base of 5th to end of 4th toe, 64. 



The largest females in the collection are only about two-thirds the size of the 

 large males; the crest is very low, all trace of it ending at about the middle of the 

 body, the foot has a proportionate length as in the males, but the head is much smaller 

 and shorter, so that from base of 5th to end of 4th toe considerably exceeds length of 

 head from anterior ear to end of muzzle; the enlarged scales of the caudal whorls are 

 relatively smaller, and the coloration is darker, with 7 narrow light bands between 

 rump and axilla more or less conspicuous. 



Measurements of No. 5640 9. — Total length, 552 mm.; tip of muzzle to 

 anus, 207; tail, 345; tip of muzzle to fold, 66; shielded part of head, 43; head width, 

 35; head width across middle of orbits, 23; axilla to nostril, 81; axilla to anterior 

 border of ear, 46; width of widest caudal whorl, 8.5; hind leg, 125; base of 5th to end 

 of 4th toe, 49. 



Comparison of the measurements of Ctenosaura townsendi, new 

 species, and Ctenosaura conspicuosa shows that the Ctenosaura on 

 Cerralvo Island is a species of considerably stouter build, with greater 

 breadth of head and shorter neck than the San Esteban form. 



2. Ctenosaura insulana, new species 



Type.— A. M. N. H. No. 2694, <?. Collector, C. H. Townsend, Albatross Expedi- 

 tion, April 19, 1911. 



Paratypes— A. M. N. H. Nos. 5641 9, 5568-5569, immature. 



Type Locality. — Cerralvo Island, Gulf of California, Mexico. 



Diagnosis. — With close resemblance in scutellation to Ctenosaura hemilopha 

 Cope, of the Cape Region. Total length often exceeding 600 mm. in the large males, 

 for which the following characters are diagnostic : high scales of the crest graduated to 

 a point on a line just posterior to the elbows, small keeled crest scales traceable about 

 two-thirds the distance to the rump; scales on dorsal tibia smooth or very weakly 

 keeled, dorsal scales on foot without spines or very shortly mucronate; tail spinous 

 to the end; scales in posterior rows of the caudal whorls very large on first half of tail, 

 length of largest equal to 14 dorsal scales, not exceeded by length of tallest scales in 



