S I B Y X X. 



The bocty is elongated, subcylindrical, being flattened beneath. 

 The tail, which forms about the fifth of the total length, is subconical 

 and tapering. The scales are perfectly smooth and imbricated, dis- 

 posed upon nineteen longitudinal series, nine of which may still be 

 counted upon the base of the tail. Those constituting the series 

 adjoining the abdominal scutellae are broad, and much larger than 

 the rest, which are sub-lanceolated, except on the second series, where 

 they assume the subrhombic shape of the outer series. The skin 

 is black. The abdominal scutellae are well developed transversely ; 

 they are one hundred and eighty-seven in number, the preanal one 

 being subdivided, broad, and convex exteriorly. The subcaudal 

 scutellae are sixty-nine in number, and disposed upon a double series. 



We have examined two specimens of this species, one measuring 

 thirty-six inches in total length, and the tail separately seven inches 

 and a half; the other, whose total length was twenty-three inches, 

 gave five inches and a half to the tail. The dorsal scales are disposed 

 upon nineteen longitudinal rows or series; the abdominal scutellae, 

 in the largest specimen, are one hundred and eighty -seven, and the 

 subcaudals sixty-nine pairs, whilst in the smallest, the abdominals are 

 one hundred and seventy-seven, and the subcaudals seventy-six. The 

 preanal scutellae being subdivided. 



The color above is olivaceous, with the base and tip of the scales 

 black, hence the appearance of transverse, oblique, black, interrupted 

 lines ; sometimes the upper region of the body has a maculated ap- 

 pearance, from the spreading of the black over the base of the scales. 

 The edges of the cephalic plates are black also. The inferior region 

 is of a uniform pale-yellow, with a black spot at the posterior and 

 external margin of the scutellae, hence a series of small black spots 

 on either side of the abdomen, and which may be traced to a certain 

 distance along the tail. 



Loc. Specimens of this species were collected on the coast of 

 Patagonia, about the mouth of the Rio Negro. 



Plate XII, fig. 1, represents Callirhinus p<itagoniensis, size of life. 



Fig. 2, is a profile view of the head. 



Fig. 3, an upper view of the head. 



Fig. 4, the same region, seen from beneath. 



36 



