ART. 23. AN EXTINCT VARANIP LIZARD GILMORE. 25 



genus Varanus^ indicating Saniwa to be a true member of the family 

 Varanidae. 



Although Leidy studied only a few of the bones of the type speci- 

 men, he more than any subsequent authority correctly diagnosed its 

 true relationships. He says : " 



The remains belong to a lacertain about the size of the existing monitor of 

 the Nile, to which it appears to be closely related. The bones indicate a 

 robust body, a long tail, and limbs with long toes. 



The vertebrae resemble those of the Nilotic monitor in form and propor- 

 tions, and like them possesses no zygosphenal articulation. 



The last statement is now known to be incorrect as there are vestigal 

 zygosphenes present on the dorsal vertebrae, but I do not consider 

 their presence of sufficient morphological importance to bar the as- 

 signment of Saniwa from the Varanidae, especially since they appear 

 to be undergoing reduction, tlms tending toward the conditions found 

 in the Varanus vertebrae, where they have entirely disappeared. It 

 was the discovery of similar reduced zygosphenal articulations of the 

 vertebrae that led Marsh" in 1872 to establish the genus Thinosau- 

 ru8, which he recognized as being closely related but distinct from 

 Saniwa because of the supposed absence of zygosphenes in that 

 genus. A careful study of Marsh's description and measurements 

 of the genotype Thinosaurus paucidens leads me to the conclusion 

 that Thinosaurus and Saniwa are congeneric. The latter being the 

 older by two years, Thinosaurus thus becomes a synonym, and the 

 described species will hereafter be designated respectively Saniwa 

 paucidens (Marsh) , S. leptodus (Marsh) , S. crassv^ (Marsh) , S. gran- 

 dis (Marsh), and ^S'. agilis (Marsh). 



It would also appear quite probable that a comparative study of 

 the type specimens on which the above species were founded would 

 show one or more of them to be referable to Saniwa ensidens Leidy. 



Tinosaurus, which Fejervary ^^ regards as being equivalent of 

 Thinosawms, probably represents a distinct genus, as is apparently 

 indicated by Marsh's meager description,-" in which the teeth are 

 described as having cusps, whereas all of the known Varanidae have 

 simple coned teeth without auxilliary cusps. 



The family Varanidae therefore contains the genus VaranvrS, 

 largely made up of living species of lizards, and the genus Saniwa, 

 which at this time includes six or more extinct species. 



'^ Leidy, J. Kept. U. S. Geol. Survey Terr., F. V. Hayden, U. S. in charge, vol. 1. 1873, 

 p. 181. 



" Marsh, O. C. Amer. Journ. Scl., vol. 4, 1872, pp. 299-300. 

 "Ann. Mus. Nat. Hung., vol. 16, 1918, p. 362. 

 s^Amer. Journ. Sci.. ser. 3. vol. 4. 1872. o. 304. 



