104 MR. F. E. BEDDARD ON THE VISCERAL [Feb. 7, 



tion of the Lacertilia with which I am acquainted there is no 

 tendency to separate the Varanidse from other Lizards, although it 

 is true that Mr. Boulenger remarks upon them as forming " a 

 perfectly isolated group " '. He does not, however, lay weight upon 

 this opinion by separating the family in any way ; it is, indeed, 

 particularly associated in his scheme with the Helodermatidse, 

 Zonuridse, Iguauidae, &c. I have not yet had an opportunity of 

 studving the structure of Heloderma ; and such papers as have been 

 published upon the anatomy of this genus do not touch upon the 

 points to which I have directed attention in this communication. I 

 cannot, however, agree to such a close association of the Varanidse 

 and Iguanidae as is proposed by Mr. Boulenger ; and other facts, to 

 which I shall direct attention presently, point unmistakably to the 

 isolation of the Varanidae, and perhaps to affinities with the CrocodiHa. 



There is little reason to doubt that the Sauropsida form a group 

 which have been derived from a single Reptilian ancestor ; this is 

 allowed by Cope ' except in so far as regards the Icthyosauria. 

 Dr. Baur^ derives all the Sauropsida from the Carboniferous 

 Proganosauria, which, in his opinion, is a group of Reptiles, though 

 Cope with some uncertainty assigns this same group to the Amphibia. 

 Both these writers concur in the belief that the Rhynchocephalia 

 {Hatteria) are the most generalized of all living reptiles, and most 

 nearly represent the primitive stock from which all existing as well 

 as extinct orders of Reptiles took their origin. 



Dr. Baur is of opinion that the existing Lacertilia (and Ophidia) 

 come nearer to this primitive stock than do any other orders of the 

 Sauropsida, while Prof. Huxley ' thinks that the differences between 

 Hatteria and other Lacertilia have been made too much of. The 

 visceral anatomy of Hatteria is certainly much nearer to that of 

 Lacerta than to any other Sauropsidan, and the Lacertilia as a 

 whole are decidedly at a much lower grade of organization, as regards 

 the viscera, than are either the Crocodilia and Aves on the one hand, 

 or the Testudinata on the other. 



These considerations render the existence of Crocodihan affinities 

 in Monitor more intelligible than might at first sight appear ; they 

 also point to the conclusion that the difference in structure be- 

 tween the Varanidae and other Lizards to which attention has 

 been here directed must liave existed in the ancestral Reptihan 

 stock which gave rise to the existing Lacertilia, Crocodilia, and 

 Aves ; I would argue, in fact, for the extreme age of a Reptilian 

 type closely allied to Far anus and Monitor. Can this type be 

 Protorosaurus ? It is a Permian Reptile undoubtedly with near 

 affinities to the existing Lacertilia, though with thecodont teeth as 

 in the Crocodilia ; it has been stated that this Lizard approximates 

 closely to the living Monitors*. 



1 Ann. & Mag. Nat. Hist. xiv. (1884), p. 117. 

 ^ American Naturalist, 1885, p. 246. 



^ Journal of Morpliology, vol. i. p. 93. " Quart. Journ. Geol. Soc. 1887. 



^ See, however, a paper on rrofomsain-us by Seelcy (Phil. Trans. 1887), who 

 does not allow any special Lacertiliaii affinities. 



