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Show ] 9 0 4 .] ANATOMY OF PELAGIC SERPENTS. 151 lung in this serpent has not the excessively thin-walled character that it has in most land-snakes. In the latter, when dissected, the anangious region of the lung seems to be little more than a space between the viscera of the posterior region of the body. In I latyurus the lung lias thick walls throughout. Examined in transverse sections, the posterior region of the lung, some way after the dilatation, is seen to be undoubtedly a, functional lung, inasmuch as the blood-capillaries are numerous and approach very near to the inner surface, being in fact only separated from it by the pulmonary epithelium. The muscular walls are very thick, especially the inner layer of circular fibres. Evidently, therefore, the lung is capable of considerable alterations in size. Dr. Cantor gives an account of the lungs of Hydrophis schistosa * Schlegel ( = Enhydrina valakadien of Mr. Boulenger's Catalogue), somewhat different from the facts as observed by myself in Platyurus colubrinus ; these differences may be doubtless put down to the circumstance that the two serpents are of different genera. In the first place, the tracheal lung would seem to be continuous with the bronchial lung, though this is not absolutely clear from Cantor's figure t. The tracheal lung is, moreover, of much less extent in Enhydrina. The pattern of the meshwork is quite different. Finally the dilatation along the course of the pulmonic portion of the bronchial lung, such as I have found in Platyurus, is less than in Enhydrina, and the extreme tip of the lung in the serpent dissected by me is not tied down to the parietes by any tag. The dilatation which he does figure is apparently part of the functional lung. ( 2) Hydrus platyurus. Of this snake the example at my disposal was a female with the ova immature. The position of the viscera has been already dealt with in considering Platyurus and a comparison of the two snakes there instituted. Alimentary viscera. -The gall-bladder, pancreas, and spleen are not unlike those of the Sea-Snake figured by Dr. Cantor J. After receiving the hepatic duct, the bile-duct plunges into the substance of the pancreas on its way to reach the duodenum. Whether it forms a rete therein or not, 1 have not ascertained ; but it is clear that there is not room for a very extensive one. The pancreas is much lobulated, and extends in front of, and behind, the gallbladder. The liver, as will be gathered from the measurements on p. 148, is actually, as well as relatively, shorter than that of Platyurus colubrinus. It is, however, of a more massive structure and is less divided by transverse furrows into " segments." I detected only four of these. The liver also appears to me to be a little closer to the heart than it is in Platyurus. The coiled region of the intestine is relatively rather shorter than in Platyurus. Kidneys.-The kidneys of Hydrus platyurus differ markedly from those of Platyurus colubrinus. They are in the first place * " Observations upon Pelagic Serpents," Trans. Zool. Soc. ii. p. 305. f Lor. rif. pi. 57. tig. 1 m. J Lor. cit. pi. 57. figs. 1, 2. |