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Show 1904.] ON TIIE ANATOMY OF CERTAIN SNAKES. 1 0 7 3. Notes upon the Anatomy of certain Snakes of the Family Boidce. B y F r a n k E. B e d d a r d , M.A., F.R.S., Prosector to the Society. [Received May 2,1904.] (Text-figures 19-23.) The Boidfe are held by most zoologists to occupy a place near the base of the Ophidian series. This view is based chiefly upon the paired lungs, the considerable rudiments of the hind limbs, and upon some other osteological points which are duly summed up by Boulenger*. The viscera also confirm this opinion; and I propose in the following pages to call attention to some new or little-known facts relating to the circulatory system which collectively support it. § Gubernaculum cordis, and Right and Left Aortce. No member of the genera Python, Boa, Eunectes, and Eryx which I have dissected possesses any trace whatsoever of a gubernaculum cordis tying down the apex of the heart to the walls of the pericardium. It is not altogether unnecessary to record the absence of a gubernaculum, though it has been stated that the Lacertilia are to be contrasted with the Ophidia by the presence in the former and the absence in the latter of this gubernaculum. A more correct statement would be arrived at if the word " generally " were interpolated in both cases. I find, in fact, considerable vestiges of this tag in several Ophidia. It occurs for example in Coronella getula. In Ccelopeltis monspessulana a thin sheet of membrane runs from the ventricle some little way above the apex to the vena cava and passes down the latter to the posterior wall of the pericardium. In the Hamadryad (Ophiophagus bungarus) the covering membrane of the heart (= visceral layer of peritoneum) is obvious and can be stripped off. Posteriorly, this membrane forms a tubular prolongation of which one side is attached to the vena cava at its entrance to the heart and to the pericardium beyond, while the other is attached to the pericardium wall behind. The ventricle, therefore, near to the apex, but on one side, is attached not merely to the vena cava, but also to the wall of the pericardium. It is impossible to speak of these structures but as a gubernaculum cordis. On the other hand, it is clear that they differ somewhat from the gubernaculum in the Lacertilia, which has no relation to the vena cava but attaches the actual apex of the ventricle to the pericardial wall, and is of more ligamentous consistency. The structure is therefore possibly a new one in the Ophidia, on which view its total absence in the Boidse (so far as the material which I have examined enables me to say) may well be * Catalogue of Snakes in the British Museum (Natural History), London, 1893. |
