18C3.] DR. J. E. GRAY ON THE GENUS STERNOTHiERUS. 193 



especially of the first vertebral shield, which have been hitherto to 

 some extent depended on for the separation of the species, are very 

 variable. Therefore the discovery of some other more permanent 

 characters seems important ; and the form and disposition of the 

 shields on the head appear to furnish such characters. 



Mr. Cope observes that S. derbianus differs from S. sinuatus of 

 Smith " mainly in the form of the upper mandible, which is ob- 

 tusely hooked in the former, bidentate in the latter." I suspect he 

 must have been misled in these observations by figures or descriptions ; 

 for the jaws of the typical specimens of the two species are very similar. 



It will be necessary to separate the genus into three sections, ac- 

 cording to the form of the head, premising that I only know the 

 species belonging to the third section from the descriptions of MM. 

 Dumeril and Bibron, as all the specimens that have come under my 

 observation belong to the first or second sections. These sections 

 may be thus characterized : — 



I. Head short and broad; the upper jaw obscurely notched and 

 bidentate in front ; the crown shielded to a line even with the 

 back of the tympanum, Tanoa. 



1. Sternoth^rus sinuatus, a. Smith, S. African Zool. t. 

 Head rather broad, depressed ; jaws pale ; the temporal plate 



Head of S. sinuatus. 



broad and short, only reaching to the front of the tympanum, and 

 with another rather smaller similar plate behind it over the ear ; the 

 hinder vertebral plate of the adult as wide as long, not tubercular ; 

 the fore legs with small scales, and with some very wide, slender, 

 band-like shields on the inner side of the upper surface ; the ster- 

 num with a narrow deep notch behind. 



Sternothcerus castaneus, part. ; Gray, Cat. Shield Rept. B.M. p. 52. 



Hab. S. Africa : Natal (Dr. Krauss). 



In other specimens the front marginal shields are rather wide, 

 the middle one as long as broad ; the front vertebral shield is elon- 

 gate, with straight sides. 



Proc. Zool. Soc— 1863, No. XIII. 



