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Show 1906.] ON T1IE VASCULAR SYSTEM OF THE HELODERM. 601 3. On the Vascular System of Heloderma, with Notes on that of the Monitors and Crocodiles. By F r a n k E. B e d d a r d , M.A., F.R.S., &c., Prosector to the Society. [Received May 11, 1906.] (Text-figures 99-106.) Although much work has been done upon the blood-system of the Lacertilia, especially by Rathke and Hochstetter *, there remain a number of important genera of which we have at present either no knowledge whatever, or the very slightest only. Among these is the genus Heloderma, with the general anatomy of which the recent investigations of Boulenger, Stewart, and particularly Shufeldt t have made us well acquainted. In the present communication I bring before the Society some facts concerning the blood-vessels of this Lizard in continuation of former contributions to the anatomy of this Order of Reptiles +. Having had the opportunity, during the last year or two, of dissecting several examples, comprising several species, of Varanus, I incorporate these notes into the present communication for the reason that Heloderma is in some respects not very remote from Varanus §, and indeed shows certain apparent resemblances to that genus in the arrangement of the blood-vessels, as will be pointed out in the course of the following pages. Since both in Heloderma and Varanus there is a departure in many directions from the arrangement of the blood-vessels found in other Lacertilia (e. g. Iguana, Sldnks, Geckos, Ophisaurus, Ampliisbcena, Anguis), and on the whole in the direction of greater complication, it seemed to me important to compare the ascertained facts with those relating to the Crocodilia, since the vascular system of the Crocodilia is perhaps the most advanced among the Reptilia. In this department I am able to add some details to the classical treatise of Rathke, in addition to the facts accumulated by Jacquart and Hochstetter, whose contributions will be referred to on a later page. Of the Crocodilia I have been able to dissect several species belonging to more than one genus. a ) On some Veins and Arteries in Heloderma suspectum. In a specimen of Heloderma suspectum which died in the Society's Gardens in January of the present year, the veins were turgid with blood, and therefore in an excellent state for anatomical observation. I had the arterial system injected, and am therefore able to give, as I trust, some reliable notices of various # Morpli. Jahrb. xix. 1893, were earlier papers are referred to. f Boulenger, P. Z. S. 1891, p. 109; Stewart, ibid. 1891, p. 119 ; Shufeldt, ibid. 1890, p. 148. X In P. Z. S. 1904 and 1905. § This is not a prevalent view though adopted by Baur. See Boulenger (P. Z. S. 1891, p. 116) for discussion of the subject. |