1182 REPORT OF NATIONAL MUSEUM, 1898. 



spaces. G-astrosteges with brown aud gray sliades at their extremities 

 at points alternating with the dorsal and lateral spots; otherwise with- 

 out markings. Tail colored like the body, buff with brown cross-bands 

 except at the extremity, where there are two black cross-bauds. 



The colors of the head are indistinct. There is a brownish-gray 

 postocular band which extends to the angle of the mouth, the superior 

 border not well defined, the inferior one a yellowish band, which is as 

 wide as the eye and reaches the labial border below it. A large spot 

 on each side of the nape above the suspensoriura of the lower jaw, 

 which sends forward a shade to the inner border of the superciliary 

 plate on each side. Superciliary aud nasal plates paler than the 

 others. 



Cat. No. 5271 differs in several respects from the types (Cat. Kos. 

 471, 472). The dorsal and lateral spots do not unite into cross bauds 

 anterior to the tail. The lateral spots are represented by traces only on 

 the anterior third of the length. The dorsal spots have brown borders, 

 while the interiors are but little darker than the ground color, and are 

 not punctulate. The interspaces are not yellow. The head markings, 

 except the postorbital band, are wanting. 



Cat. Nos. Scales. Upper labials. Gastrosteges. Urosteges. Length. Tail. 



'>nm. mm. 



5271 (rattle cut off) 25. 14. 170. 23?+. 653. 45+? 



471 23. 14. 170. 21. 



The large number of specimens of this species obtained by the Death 

 Valley exploring expedition enables me to add considerably to the 

 knowledge of its characters. The division of the supraorbital plate is 

 present in all of the new specimens, but in various degrees. It is indis- 

 tinctly indicated in one of the types, and may have been indicated 

 in the other, but have been obliterated by long soaking in weak 

 spirits. This division, when comj)lete, is into three parts — an anterior 

 smaller and a posterior larger, and a still smaller marginal, produced 

 by the bifurcation of the transverse suture. This marginal scute is fre- 

 quently only half defined. This structure is, in some of its conditions, 

 probably similar to that which gave origin to the horn of the C. cerastes^ 

 which is a prolongation of a fold of the supraorbital plate defined by 

 two grooves. The number of loreal plates varies from one to three, 

 but one is the more common number. 



This species is nearest the G. enyo Cope of the Lower Californian 

 Peninsula. It differs from that species in the smoothness of the head 

 scales, which are strongly carinate in G. enyo; also in the presence of 

 keels on all the body scales, except sometimes one row, instead of the 

 five and six smooth rows on each side. The color is materially different, 

 since the G. tkiris is a pale form apparently adajtted to desert surround- 

 ings, while the colors of the G. enyo, especially the head bands, are 

 bright and strong. The i)attern is not very different, but the lateral 

 angles of the dorsal hexagons have a black apex in the G. enyo, which 

 is wanting in G. tigrin, and head bands are wanting or very indistinct. 



