NATURAL SCIENCES OP PHILADELPHIA. 49 



the Loo Choo islands. The African genus differs in no respect from the Asiatic, 

 except in the presence of the small plate imbedded between the inter-nasal and 

 frontal and the two fronto-nasals. 



Fam. CHALCIDIANS or CYCLOSAURIANS. 



(Sub-fam. Ptycliopleuri.) 



There are two specimens of Gcrrhosnurus in the collection of Dr. Ford, one 

 much smaller than the other and jjrobably the young. The Larger one resem- 

 bles in its coloration Gerrhosaurus Bibronii, of S. Africa, but the measurements 

 differ both from those of that species and of typicus. 



Inches. Lines. 



Length from nose to base of tail 3 6 



Of tail 7 9 



From nose to meatus externus 9 



From nose to base of anterior extremities 1 4 



Distance between fore and hinder extremities 2 



These dimensions more nearly correspond with those of flavigularis, but in 

 that there are ten rows of ventral scutes. 



G. validus is a much larger species, and sepiformia and subtessellatus do not 

 in the least resemble it, (vide Smith, Illustrations of the Zoology of S. Africa.) 

 We therefore consider these two specimens as belonging to a new and un- 

 described species, with the following characters: — 



Gerrhosaurus nigro-lineatus. 



Char. Eight rows of ventral scutes; six superior labials ; body slender; tail 

 long, two yellowish vittae, one on each side of the back, commencing at the 

 occiput and lost upon the tail; within each vitta a black band running the 

 whole length of the back ; the interspace marked with black spots assuming more 

 or less the form of longitudinal lines well marked upon the tail ; flanks, in the 

 young white spotted, under parts yellowish. 



Description. The body is slender, covered above and upon the sides with 

 twenty-five longitudinal rows of carinated scales; the interspace between these 

 and the ventral scutes occupied with six rows of granulations ; tail long and 

 tapering, cyclo-tetragonal at base ; the rostral plate presents an acute angle 

 above, and articulates on either side with the first labial and the naso-rostral ; 

 the nostril opens between three plates, the naso-rostral, the naso-frenal and 

 the first labial ; the naso-rostral are well developed, in contact, with a convex an- 

 terior margin, the internal quite short, the posterior concave, where they articu- 

 late with the inter-nasal ; the naso-frenal are in contact inferiorly with the first 

 supra-labial, above with the inter-nasal ; the inter-nasal is a large plate, more 

 extended laterally than longitudinally, its inferior and lateral margin in contact 

 with the first frenal ; the fronto-nasals are tw'o in number and in contact ; 

 the frontal is hexagonal, longer than broad, more narrow posteriorly, its lateral 

 margins excavated ; there are two fronto-parietals, a little larger than the fronto- 

 nasals, and like them pentagonal ; there are two large parietals, with a small 

 inter-parietal, broader anteriorly; the second frenal is much larger than the 

 first ; there are two small freno-orbitars, the first longer than the second ; there 

 are four supra-orbitars, with a longitudinal row of as many plates beneath 

 them, and there are six supra-labials ; the posterior geneials are considerably 

 larger than the anterior ; the mental is broader than long ; there are eight longi- 

 tudinal rows of quadrangular ventral scutes, more or less striated, and fourteen 

 anal pores on each side ; the preanal scales are five in number, the lateral ones the 

 most developed ; scales upon outer surface of thighs, legs and forearms strongly 

 carinated ; there are thirteen transverse rows of scales between the occiput and 

 the anterior extremity; the total number between the occiput and the posterior 

 extremity fifty-one; one hundred and eleven verlicillas upon the tail ; auricular 

 opening triangular, with a large scale in front; eight scales upon right temple, 

 nine on left, in three rows, the posterior of the middle row the largest. 



1857.] 4 



