SPECIES OF THE GENUS XANTUSIA. 533 



Xantusia riversiana Cope. 



Xantusia riversiana. 



18S3, Cope, Proc. Ac. Nat. Sci. Phila., p. 29. 

 1889, Elvers, Am. Nat., xxiii, p. 1100. 

 1889, Cope, Proc. U. S. Nat. Mus., p. 147. 



Descri-ption. — The limbs are very short, and the bod}^ 

 is somewhat depressed. The upper surface of the head 

 is very flat. The nostril is pierced in a small scute at the 

 junction of the rostral, internasal, postnasal, and first la- 

 bial plates. The rostral is broad and rather low, bounded 

 by the first labial, nasal, and internasal plates. The two 

 internasals are followed by a large hexagonal frontonasal. 

 Behind this are two prefrontals, bordered posteriorly by 

 the broad frontal and the first superciliar}'- and first supra- 

 ocular plates. Each of the two frontoparietal plates is in 

 contact with the frontal, second, third and fourth supra- 

 oculars, parietal, interparietal, and its fellow of the op- 

 posite side. The interparietal is bordered behind by the 

 two large occipitals, which are separated from the parie- 

 tals by two small scutes. There is a row of large supra- 

 temporals along the outer edge of the occipital and parie- 

 tal plates. The two large loreals are in contact below 

 with the supralabials, and above with the frontonasal and 

 prefrontal plates. The eye is surrounded by a series of 

 small plates, the upper five of which are the superciliaries. 

 Between this ring and the posterior loreal are two or three 

 small plates. A series of four supraoculars separates the 

 superciliaries from the frontal and frontoparietal plates. 

 There are five superior and four or five inferior labials to 

 a point below the pupil. The eye is large, without lids, 

 and with vertical pupil. The ear has a weak anterior 

 denticulation. The inferior labials are in contact with 

 the large sublabials. The first pair of the latter are in 

 contact on the median line. The back, sides, upper and 

 posterior surfaces of the limbs, and the gular regions, are 



