OP HID I A. 



DESCR. The head is elongated, very much depressed, nearly plane 

 on the occipital, interoculary, and frontal regions, whilst it is declivous 

 towards the loral region. The extremity of the snout is truncated 

 from outwards inwards, so that the upper jaw is seen projecting 

 beyond the lower. The mouth is deeply cleft. The eyes, subcir- 

 cular in shape, are well developed, situated on the sides of the head, 

 with the longitudinal diameter a little longer than the vertical, whilst 

 the pupil is vertically elliptical. The cephalic, scale-like plates, are 

 carinated, and provided moreover with a few very minute tubercles. 

 The rostral plate is- broader than high, does not extend to the upper 

 surface of the snout, is rounded upon its upper margin, which is wider 

 than its lower margin. The nostrils are situated sideways, in the 

 middle of a single plate. The plates upon the fronto-nasal region are 

 considerably larger than on the occipital region, where they are quite 

 small. The orbit is formed by a complete circle of subquadrangular 

 plates, nearly equal in size, except one anteorbital, which is larger 

 than the others. Three or four subquadrangular plates, disposed 

 upon one series between the anteorbital and the nasal, are generally 

 well developed and diminishing in size forwardly ; or else the phrenic 

 region is covered with plates similar in size and shape to those of the 

 upper surface of the head, and disposed upon two series. A third 

 series is composed of two or three small plates, situated above the 

 fourth and fifth labials. The upper labials are ten or eleven in 

 number; the fifth and sixth being situated under the eye, but are 

 excluded from the orbit ; the second, third, fifth, and sixth are the 

 largest ; the first, fourth, and seventh are next in size, the remain- 

 ing ones becoming gradually smaller towards the angle of the mouth. 

 The symphyseal is very much developed, larger than any of the lower 

 labials, broadest towards the tip of the jaw, tapering and rounded 

 posteriorly, and slightly concave laterally. There are about twelve 

 lower labials, the anterior one entirely separated from its fellow by the 

 symphyseal. The anterior six are elongated vertically ; the remain- 

 ing ones quadrangular, diminishing in size posteriorly. We observe 

 four pair of small, scale-like, mental shields, divided by a longitudinal 

 groove. The scales under the throat are slender and elongated. 



The body is much deeper than broad, and convex above, whilst it 

 is flattened along the abdomen. The dorsal scales, disposed upon 

 thirty-two or thirty-eight longitudinal series, are all carinated, except 

 the series adjoining the abdominal scutellae, where the scales are broad 



