Vol. I] VAN DENBURGH—SNAKES OF THE GALAPAGOS ISLANDS 329 



more than two hundred gastrosteges bear scales with two pits. 

 They also have scales with no pits, and usually others with 

 one pit. In some cases large scales on the tail have three or 

 four pits. While these pits, therefore, are not of generic 

 value, they are of great use in the separation of species, as 

 shown in the following: 



Key to Galapagos Species of Dromicus 



a. — No scale-pits. 



b.— Gastrosteges more than 195 (203-214). 



c. — General coloration in spots; scales in 19 rows. Charles and 

 Gardner-near-Charles. 



Dromicus biserialis. — p. 336. 

 C.2 — Striped, the stripes fading out posteriorly; scales in 17 or 19 

 rows. Hood and Gardner-near-Hood. 



Dromicus hoodensis. — p. 338. 

 b.2— Gastrosteges fewer than 195 (169-183). 



cc. — Postoculars two; no longitudinal light stripes. Duncan, 

 Albemarle, Narborough. 



Dromicus slevini. — p. 351. 

 CC.2 — Postoculars normally three (rarely two) ; longitudinal light 

 stripes present. Jervis, South Seymour, Indefatigable. 

 Dromicus stejndachneri. — p. 353. 

 a.2 — Scale-pits present. 



bb.— Gastrosteges more than 210 (213-252). 



ccc. — Gastrosteges usually not more than 232 (213-236). James, 

 Jervis, Harrington, Indefatigable, South Seymour. 

 Dromicus dorsalis. — p. 341. 

 ccc.2 — Gastrosteges not fewer than 236 (236 to 252) ; prominent 

 light markings on nape spots or transverse blotches, 

 d. — Usually striped ; light nuchal blotches and a series of dark 

 spots on tips of gastrosteges and on lower lateral scales 

 very distinct. Narborough. 



Dromicus occidentalis. — p. 347. 

 d.2 — Spotted, without longitudinal light stripes; no series of 

 definite rounded blackish spots on lateral scales of first 

 and second rows ; light nuchal markings less prominent. 

 Albemarle and Brattle. 



Dromicus occidentalis helleri. — p. 349. 

 bb.2— Gastrosteges fewer than 210 (178-201). Chile and Peru.i 



Dromicus chamissonis. 



The Material for this Study 



It will be seen that I have recognized seven kinds of land 

 snakes from the Galapagos Archipelago. This has been made 



^ There can be little doubt that more than one species occurs in Chile and Peru. 

 The wide range in the number of gastrosteges would indicate this, and Dr. Boulenger, 

 who most kindly has examined the scale-pits in the specimens in the British Museum 

 in response to my request, writes me that most of the Chilian and Peruvian specimens 

 have scales with single pits, while those from Chiloe have scales with two pits. These 

 specimens from Chiloe doubtless represent a distinct species, as yet unnamed. 



