328 S A U R I A. 



covered with minute scales or granules : te thigbs being either wholly 

 granular or else exhibiting a patch of small scales near the base of the 

 tail. 



The tail itself is either long or moderate, depressed at the base, coni- 

 cal posteriorly, and tapering into a point, protected by carinated and 

 subverticillated scales, of various forms, though even aspect. 



The species which come under the above heading having become 

 quite numerous, writers have felt the necessity of subdividing the 

 genus into minor groups or subgenera, according to secondary traits 

 of organization, or rather zoological structure. 



Being cast, as it were, in the same mould, their structural characters 

 are multifold, and considerably interwoven, as is generally the case, at 

 large. The association of these characters will not allow an absolute 

 line of demarcation to be drawn between all the minor groups. Some- 

 times one series of characters and sometimes another series is to guide 

 the zoologist in the divisions he is about to establish. 



In the following systematic arrangement, we have endeavored to 

 remain faithful to the natural method, and, we hope, not without 

 success. Certain species on the confine of their division may some- 

 times appear as though entitled to enter one group as readily as 

 another, but we are satisfied that when the species shall have been 

 better investigated in that respect, the characters which we assign to 

 each division will only gain in strength and permanency. New species 

 may be added, requiring the establishment of new divisions, without 

 invalidating those which are now proposed. 



Whether the subgenus Sauridis, of Tschudi,* is really distinct from 

 those hereinafter treated of, we are not prepared to tell. The absence 

 of palatine teeth would, in itself, be a valuable character, should it be 

 proved that they exist under all circumstances elsewhere in the same 

 group. The rest of its diagnosis alludes to nothing peculiarly distinct 

 from characters assigned to other genera. By the folds of its neck, it 

 reminds us of either Ptychodeira or Rhytidodeira, and by its cephalic 

 plates, mayhap, somewhat Eulaemus. As to S. modestus, the only 

 species so far referred to it, being described simply in its coloration, it 

 would be idle to attempt tracing out its affinities with the numerous 

 species of the group we are now to pass in review. Tschudi seems to 

 hold it closely related to Tropidurus oxyceplialus, of Wiegmann : hence, 

 the aflBnities of Sauridis would be with Rhytidodeira. 

 * Faun. Peruan. Herp. 1845, 34. 



