638 



Bulletin American Museum of Natural History 



IVol. XLVI 



Crotaphytus dickersonse, ' new species 

 Diagnostic Characters. — Closely related to Crotaphytus collaris baileyi Stej- 

 neger, from which it is distinguished by having the hind leg considerably longer than 

 the body, a longer, more distinctly compressed tail, and slightly enlarged scales on the 

 mid-dorsal line of the tail. 



Range. — Known only from the type locality, Tiburon Island. 

 Type— U. S. N. M. No. 64451, 9 , Tiburon Island; April 12, 1911, C. H. Town- 

 send, collector (Albatross Expedition) . 



Fig. 2. Lateral and dorsal views of the head of the type of Crotaphytus dickersonse, new species 

 U.S. N.M. No. 64451, 9. X Hi 



Description of Type. — 



Habitus of Crotaphytus collaris, but legs and tail markedly longer; hind leg reach- 

 ing considerably beyond the snout when laid along the body; tail more than twice as 

 long as the head and body. Scales of the supraorbital semicircles distinct, as in C. 

 collaris baileyi; supraoculars small, occipital slightly enlarged, separated from the 

 supraorbital semicircles by two rows of smaller scales. Auricular opening narrow, 

 oblique, bordered in front by small tubercular scales directed away from the opening. 

 Ventral scales very small, not one-half the size of the ventral caudals. Soles of the 

 feet with a few keeled, tridentate, more or less mucronate scales. Tail compressed 

 with one or two median dorsal scale rows slightly enlarged. Femoral pores 19. 



Two black collars, separated by a white band, the posterior wide, complete dor- 

 sally, and ending at insertion of the arm, the anterior extending to unite on the mid- 

 line ventrally. Dorsal surface bluish gray with broad reticulating bands of darker 

 color. More or less regular transverse rows of small white spots. Tail with dark 

 spots proximally. A gular patch and groin patches reddish brown. 



Total length, 313 mm.; tail, 218 mm.; snout to posterior border of ear, 30 mm.; 

 width of head, 22 mm.; hind leg, 99 mm.; tibia, 37 mm. The tail forms .70 of the 

 total length. 



•Named for Miss Mary C. Dickerson, former Curator of the Department of Herpetology of The 

 American Museum of Natural History. 



