1881.] LIZARDS FROM ECUADOR. 229 



Peters as Gercosaura {Pantodactylus) argulus. Although the 

 number and arrangement of the prseanal scutes affords a conspicu- 

 ous and important character in the family Cercosauridae, and in many 

 cases a reliable one, sufficing, for instance, to distinguish several 

 species of Leposoma (rem the original one of Spix, and from the new 

 one recently described by Prof. Peters, allowance must be made for 

 a certain amount of variation in this particular, more especially as 

 corresponding variations in other characteristic portions of the scu- 

 tellation are to be found in the Lizards of this and closely allied 

 South-American groups. 



I have already noticed that the internasal plate is sometimes 

 entire and sometimes bisected m Neusticurus ecp/eopus, Cope, although 

 this species was described by Prof. Cope as differing from N. bicari- 

 natus, L., in having it entire (see 'Ann. N. H.' Oct. 18/9, p. 295). 

 I found also in N. bicarinatus an irregular additional praefrontal 

 plate associated with the cleft internasal. In the present series of 

 specimens of Gercosaura {Pantodactylus) argulus, the internasal 

 has a longitudinal cleft in a line with the suture of the fronto-nasals, 

 and occasionally the above-mentioned supernumerary plate is pre- 

 sent in exactly the same position as in Neusticus bicarinatus. The 

 fronto-nasals are iu that case reduced to smaller triangular and more 

 lateral plates, quite se|.arated from each other, instead of being large 

 and extensively in contact. These two forms of arrangement of the 

 nasal shields are associated with two distinct types of prseanal scu- 

 tdlation. One specimen with the additional praefrontal has four 

 narrow marginal prseanals ; another with the normal nasal plates 

 has only two large rounded marginal prteanals, like Gercosaura ocel- 

 lata, while the others have the normal nasals and the four narrow 

 marginal praeauals. 



As Prof. Peters had only a single specimen from Bogota, 

 and those in the })resent collection from Ecuador show a range of 

 variation within recognizable specific limits, I give the following 

 supplementary description : — 



3. Cercosaura (Pantodactylus) argulus, Peters, Abb. Ak. 

 Berl. 1863, p. 18-4, pi. i. fig. 3. 



Internasal broad, single, or bisected in a line with the suture of 

 the two good-sized fronto-nasals when these are extensively in con- 

 tact ; sometimes an intermediate small praefrontal joining the frontal 

 and the internasal. Frontal and fronto-])arietals of the ordinary 

 shape, interparietal large, flanked by two large parietals, and fol- 

 lowed by a small occipital enclosed between two good-sized postoc- 

 cipital plates. Nasal rather large, followed by a single i.irge frenal. 

 Supralabials six, none particularly elongate; infralabials five, the third 

 very elongate. Two pairs of large postmentals in contact, the third 

 smaller, separated by the group of large and small intervening gular 

 scales. Two contiguous rows of larger plates to the chest, where a 

 small collar is formed by a central and two lateral rounded plates. 

 Some convex scales behind the occiput ; scales of the back not very 

 narrow, keeled, pointed, the keels being sliglitly produced ; on the 



