468 Bulletin American Museum of Natural History [Vol. XLI 



This species, while very distinct, shows relationship with the forms 

 known as S. zosteromus Cope and S. magister Hallowell. 



Sator, new genus 



Type. — S grandavus, new species. 



Diagnosis. — Body strongly compressed with high vertebral ridge in the adult; 

 ziphisternal and poststernal ribs at acute angles with the vertebrae forming extremely 

 long latero ventral loops nearly or quite to the groin and recurved to the mid-ventral 

 line; a sternal fontanelle. Nostrils superior; lateral teeth tricuspid, no pterygoid 

 teeth; labials segmental, superciliaries imbricated; head scales large, as in Scelo- 

 porus and Uta; tympanum exposed. Lateral area granular, extending high on 

 shoulder and nape, strongly developed postauricular folds, and a well-developed 

 lateral fold to the groin. Scales on posterior femur granular, also on exterior aspect 

 of tibio-tarsal joint; also imbricated scales on knee and on dorsal aspect of tibia 

 differentiated, smaller and larger respectively. A strong structural gular fold usually 

 present, marked by differentiation of scales, homologous with anterior fold of 

 Holbrookia and of the Utas which have two structural folds; a posterior fold possible, 

 in some species indicated at the sides of the neck by a transverse extension of granules 

 and 2 or more enlarged scales of a "denticulated border." Tail compressed, very 

 long; caudal scales verticillate, obliquely keeled, dorsally at least with high sharp 

 keels; long series of femoral pores; hind legs very long; digits with keeled lamellae 

 inferiorly; enlarged postanals in male. 



Cope in 1888 (Proc. U. S. Nat. Mus., p. 397, PI. xxxvi, figs, la-g) 

 described a new genus, Lysoptychus (type species lateralis, from one 

 specimen collected at San Diego, Texas), supposed to be between Uta 

 and Sceloporus, the distinctive character being .a gular fold. But the 

 fold in the specimen in question is not marked structurally; it is similar 

 to the fold in Callisaurus and certain Utas resulting from looseness of 

 skin in the gular region, without structural differentiation and disappear- 

 ing when the head is bent to a horizontal with the body. Lysoptychus 

 was not recognized by herpetologists and the specimen has been re- 

 ferred to Sceloporus couchii Baird (type, U. S. N. M. No. 2739, from Santa 

 Catarina, Nuevo Leon, Mexico) (Stejneger and Barbour, 1917, Check 

 List, p. 53). 



The genus Sator represents what is evidently an ancestral form, 

 kept in existence through isolation under favorable conditions in a rel- 

 atively unchanging habitat. It combines the compressed body and 

 long compressed tail of arboreal types with many of the characters of 

 the primitive terrestrial genus Sceloporus, and also with characters, 

 such as the anterior and posterior gular folds, diagnostic of very different 

 terrestrial forms like the Utas and the Holbrookias. 



A connection of the new genus with Sceloporus exists in a Mexican 

 species, S. utiformis Cope, 1864, from Colima (a series of which is at 



