I^ orth-ioester n Argentine and Bolivia. 459 



anterior part of the body a series of oblique dark stripes are 

 seen runnino- from the back and sloping down the sides in a 

 backward direction. These stripes are regularly arranged 

 and are formed in such a manner that the tip and more or 

 less of the upper part of every third scale is blackish. Poste- 

 riorly the body and the tail are uniformly bronzy. The 

 upper head-shield bluish, mottled with bronzy and black- 

 edged. Upper labials and lower parts, including the outer 

 row of scales, whitish, but posteriorly and under t!ie tail the 

 colour becomes more greyish. 



The only specimen was collected at San Miguel. It 

 measures 36 centim. 



Liophis poacilogyrus^ Wied. 



Six (mostly young) specimens from Tatarenda, Bolivian 

 Chaco. 



Xenodon Merremii (Wagler), Blgr. 



Several specimens from Tatareuda. 



The largest specimen measured 94 centim. This and 

 three others had the usual spotted appearance. A fifth 

 specimen, measuring 82i centim. in length, does not show 

 any markings at all, being uniformly light brow^u above and 

 dirty yellowish beneath. The next smallest specimen, 

 measuring 63 centim. in length, has the markings very well 

 developed and shows a remarkable likeness in pattern and 

 mimicry to Lachesis Nemoiedi, which lives in the same region. 

 The youngest specimen, measuring about 31| centim., has the 

 cross-bands constricted in the middle only in the anterior part 

 of the body. The small spots of the lateral series become on 

 the posterior part of the body and the tail confluent into a dark 

 stripe. 



Lystrophis semicinctus, Dum. & Bibr. 



Three specimens from Crevaux, near Pilcomayo, Bolivian 

 Chaco, and others were observed at different places. 



Rliadincva sagitllfera (Jan). 



Numerous specimens from Tatarenda and Crevaux, 

 Bolivian Chaco. 



The specimens agree as regards their coloration with 

 Peracca's * description^ the large individuals having the back 



* Boll. 3Ius. Zool. Anat. Comp. Univ. Torino, vol. xii. (1897). 



