CROCODILIANS, LIZARDS, AND SNAKES. 723 



tical. Nostril between two plates, the anterior in contact with that of 

 the opposite side upon the median line. Frontonasal suture extensive. 

 Posterior to these, the ui)per surface of the head is covered with smooth 

 scales. Labial plates without pits. Scales smooth, broad, i)oreless. 

 Spurs conspicuous. Gastrosteges narrow. 



In this genus the tail is less prehensile than in Boa, but is more so 

 than in Erij.r and Charina. It also differs externally from the latter 

 genus (with which Garman at one time proposed to unite it) in the 

 absence of the frontal plate and the i^arietals adjacent to it. An impor- 

 tant osteological difference is the presence of the coronoid bone, which 

 is wanting in Chariyia. 



The species of this genus are variable in their details both as to 

 squamation and coloration. I distinguish three species. Dr. Stejue- 

 ger has named another, which he subsequently withdrew. In his latest 

 study of this genus this author distinguishes the species as follows: 



A. Eye large; its diameter more than oue-third distance from anterior cauthus to 

 tip of muzzle ; gastrosteges about 218. 

 Whitish with three blackish brown longitudinal bands in strong contrast. 



L. trivirgata. 



AA. Eye smaller; its diameter one-third or less the distance from anterior canthus 



to tip of muzzle; gastrosteges 224 to 241. 



Color brownish or bluish above, with or without longitudinal bands, which 



when present contrast but little with the ground color ; true loreals 3 ; scale 



rows 39-43 ; rostral not prominent L. roscofusca. 



Color as above; true loreals 2; scale rows 35; rostral prominent L. orcutti. 



LICHANURA TRIVIRGATA Cope. 



Lichanura trivirgata Cope, Proc. Acad. Nat. Sci. Phila., 1861, p. 304. — Bocoi:rt, 

 Miss. Sci. deMex., p. 513. — Stejneger, Proc. U. S. Nat. Mus., 1889, XII, p. 98. — 

 BouLENGEK, Cat. Snakes Brit. Mus., 1, 1893, p. 129. 



Lichanura myriolepis Cope, Proc. Acad. Nat. Sci, Phila., 1868, p. 2. — Stejneger, 

 Proc. U. S. Nat. Mus., 1889, p. 96. 



Lichanura sim2)lex Stejneger, Proc. U. S. Nat. Mus., XII, 1889, p. 98. 



Scales of the body in forty to forty-five longitudinal rows, the inferior 

 a little larger than the others. Eight to ten scales in the ocular ring; 

 superior lal>ials fourteen or fifteen, the anterior three highest. Loreals, 

 three superit. r vertical, two inferior horizontal. Ro.stral plates slightly 

 prominent, ele zated, recurved, quinquelateral, its labial border as long 

 as its nasal. In/arior labials fifteen, the anterior five longest. A short 

 mental fissure. 



General color pale yellowish, tinged with brown. The belly and 

 flanks are irregularly specked with liver brown. Superiorly there 

 extend from the muzzle to the end of the tail three deep liver brown 

 bands, the median four and the two lateral, five scales wide, separated 

 by intervals three and a half scales in width. 



The coloration of this handsome boa is altogether unique in the 

 family. It calls to mind the Salvadora of the same region. It inhabits 

 the southern region of Lower California, where Mr. J. Xautus has 



