214 ZOOLOGY. 



Descr. The head is suhovoid, heing depressed upon its upper surface; the snout is rounded, 

 and the eye, subcircular in shape, is of moderate development, its diameter heing equal to the 

 ■width of the vertical plate upon the middle of its length. The vertical plate is large and sub- 

 pentagonal, either slightly concave upon its sides or linear; its posterior extremity heing 

 moderately angular. The occipitals are a little shorter than the vertical, hut anteriorl}' nearly 

 as broad. The postfrontals are broader than long, extending but little to the sides of the head, 

 being posteriorly rounded. The prefrontals are subtriangular, irregularly rounded off, and do 

 not reach the nostrils. The rostral is subconical, concave beneath. The nostrils are small 

 and subelliptical, situated between two plates the sutures of which are sometimes obliterated 

 either above or below these apertures. The loral is quadrangular and larger than either the 

 post or prenasals, which have the same general shape. There are two anteorbitals ; the upper- 

 most is longer than high, and a little longer than the lower one, which is rather narrow and 

 elongated ; also two postorbitals nearly equal in size and similar in shape. The temporal 

 shields, seven or eight in number, are so small and so much like the scales, that there are only 

 two that may readily be distinguished from the latter by their shape. The iipper labials are 

 seven in number : the fifth being the largest, the sixth is the next in size, then the fourth, the 

 third, and the second ; the seventh is a little larger than the first, which is the smallest of all. 

 The third and fourth constitute the inferior rim of the orbit ; their suture being situated beneath 

 the pupil. The symphyseal is triangular ; the lower labials, being nine in number, diminish in 

 size both forwards and backwards from the fifth, which is the largest of all ; the seventh, eighth, 

 and ninth are rather narrow and elongated, whilst the four anterior are higher than long. 

 The first one in particular is nearly twice the height of the second, and separates entirely the 

 symphyseal from the anterior mental shields, of which it assumes the general feature. There 

 are two pairs of mental shields of about the same length, but the posterior pair is more slender 

 and posteriorly subacute. 



The body is subcylindrical, thickest upon its middle, tapering both posteriorly and anteriorly 

 ■where a somewhat contracted neck separates it from the head. The tail is subconical, pointed 

 posteriorly, rather short, constituting about the sixth part of the entire length. The scales 

 are smooth, disposed upon nineteen longitudinal series ; they are subacute posteriorly, and 

 largest upon the external series, gradually diminishing hence to the central or dorsal series. 

 On the nape and under the head they are the smallest. The abdominal region is rather nar- 

 row. There are one hundred and fifty-five abdominal scutellas^ the posterior one being bifid, 

 and forty-three subcaudal scutellie, all of which bifid. 



Abd. sc. 154+ 1. Subc. sc. 43. Dors, rows 19. Total length 15 inches and ^o ', tail 2| inches. 



The ground-color appears now olivaceous brown above, yellowish beneath. The anterior 

 margin of the abdominal scutellre being jet black with a subtriangular blotch upon their middle 

 region, and occasionally also upon their extremities, the lower surface of the body may assume 

 quite a maculated appearance. The anterior margin of all the scales is black, but when in 

 their normal and imbricated state, the black is not seen externally except ujjon the fourth and 

 eight series on either side, thus constituting two pair of obsolete vittse. The middle dorsal 

 series exhibits likewise the black margin of its scales, though in a less conspicuous manner as 

 the specimens grow to a larger size. In the very immature condition almost every scale shows 

 its black edge, constituting irregular zigzag lines. The dorsal vitta3 sometimes assume the ap- 

 pearance of a series of double crescents contiguous upon their convexity : this is owing to the 

 fact of the black extending along the sides of the scales. The lateral vittfe, from the neck 

 ascend to the occipital region of the head, the sides of which are marked by two narrow black 

 stripes, the upper one slightly arched, extending from the posterior rim of the orbit to the angle 

 of the mouth; the other runs obliquely from the lower rim of the orbit, across the fourth and 

 fiifth labials to the edge of the mouth. 



This species was collected in the vicinity of Santiago, Chile. 



