1904.] ANATOMY OF PELAGIC SERPEXTS. 151 



lung in this sei|:)ent has not the excessively thin-walled character 

 that it has in most land-snakes. In the latter, when dissected, the 

 anangiovis region of the lung seems to be little more than a space 

 between the viscera of the posterior region of the body. In 

 Platyurus the lung has 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 ai-e numerous and apjjroach very 

 near to the iniiei' surface, being in fact only separated from it by 

 the pulmonary epithelium. The muscular walls are veiy thick, 

 especially the inner layer of circulai- fibres. Evidently, therefore, 

 the lung is capable of considerable alterations in size. 



Dr. Cantor gives an account of the lungs of Hydropliis schistosa ^ 

 Schlegel { = Enhydrina vcdakadien of Mr. Boulenger's Catalogue), 

 somewhat different from the facts as observed by myself in 

 Platyurus cohihrinus ; these differences may be doubtless put down 

 to the circumstance that the two sei-pents 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 

 23ortion 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 serjjent dissected by me is not tied down to the paiietes by 

 any tag. The dilatation which he does figui-e is apparently pai-t 

 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 Platyi'.rihs 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. Aftei-^ 

 receiving the hepatic duct, the bile-duct plunges into the substance 

 of the panci-eas on its way to i-each the duodenum. Whether it 

 forms a rete therein or not, I 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 gall- 

 bladder. The liver, as will be gathered from the measurements 

 on p. 148, is actually, as well as relatively, shorter than that of 

 Platyurus coltibrimis. It is, however, of a more massive structure 

 and is less divided by transverse furrows into " segments." I 

 detected only four of these. The livei' 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 coluhrinus. They are in the first place 



* " Observations upon Pelagic Serpents," Trans. Zool. Soc. ii. p. 305, 

 t Ijoc. cit. pi. 57. fig. 1 m. " X Loc. cit. pi. 57. figs. 1, 2. 



