1904.] AXATOMY OF PELAGIC SERPENTS. 149 



division of the livei- by fui-i'ows i-uuning ;it right angles to the 

 longitudinal axis of the body — is more mai'ked. I counted five of 

 these transverse furrows, which vaiy in depth and divide the 

 hver into a series of segments of hepatic substance. As I shall 

 point out later (see p. 151), Hydrus plati/nrus shows the same 

 " segmentation " of tlie liver. Milne-Edwards observes* of the 

 liver of TyjMops that it is " divise en lobes plats," and this 

 lobation is figured also by Cope t ; but it does not appear to be by 

 any means so regular as in Platyurus. One cannot but put down 

 this marked lobation to the regular bending of the body in 

 swimming, and it forms an example of " segmentation " pi-obably 

 tiuceable to a definite mechanical cause. 



The gall-bladder gives ofi:' a single duct which soon forms a very 

 complicated netwoi-k in connection with the hepa,tic duct. This 

 network is very much more complex than in Hydrus, and the rete 

 of ducts is so long before it enters the duodenum that the gall- 

 bladder can be dissected out and pulled much further away from 

 the alimentary canal than is possible in Hydrus. The pancreas 

 seems to me to be smallei- propoi-tionately (it certainly is so 

 actually) than in Hydrus. The coiled region of the intestine is 

 veiy long. When the coils are left undistui-bed within their 

 crelomic space, they measure | of an inch, but when unwrapped 

 no less than 5 inches. The kidneys are appi'oximately equal in 

 size, each measuriiig about 4 inch in length. They are broad in 

 proportion to their length, and almost suggest those of the Bold 

 Eryx. The right, anterior, kidney hardly at all overlaps the left, 

 which commences where it ends. 



§ Lung. 



It has been pointed out by several zoologists, including Cope J, 

 that Flatyurus and some other genera of Sea-Serpents possess the 

 tracheal lung found also in a few genera of terrestrial Colubrines. 

 Cope's statement on the matter is as follows : — " Finally the 

 ti-a,cheal lung, as I shall call it, is distinct from the true lung in 

 Platyurus and in Chersydrus. In the former of these genera, the 

 trachea is not separate from the lumen." I do not think, however, 

 that any detailed description of the lung exists. I shall endeavour 

 thei-efore to supply this omission by the following description. 

 There is no trace that I could discover of a second lung. The 

 single lung extends to within one inch of the cloacal aperture and 

 ends abruptly without any special diminution of calibre. It lies, 

 posteriorly at any rate, on the right-hand side and is firmly boinid 

 to the dorsal paiietes. 



The tracheal lung is, as Cope says, distinct from the bronchial 

 lung ; the two ai-e separated at the end of the one and the 

 beginning of the other by one of the pulmonary vessels which 

 passes between them. The tracheal king begins very high up 

 in the body, close behind the head ; it ends posteriorly jiist in 

 front of the origin from the heart of the right aortic arch. 



* ' Leij'ons suv la Physiologic et rAiiatomie coniparee.' 



t " On the Lungs of the Ophidia," Proc. Amer. Phil. Soc. xxxiii. 1894. 



X Loc. cit. p. 217. 



