530 MR. F. B. BEDDARD ON THE VASCULAR AND [May 1, 



and then the restriction of the membrane left ; or, firstly the re- 

 duction in diameter of the lung and then the disappearance of 

 the lung-tissue. That degeneration of this kind should occur in 

 more than one way is not surprising. It may be obviously 

 matched by parallel instances. 



It is well known that among the Boidfe, for example, the lung, 

 or lungs, extend, like those of Lizards, beyond (^. e. headwards of) 

 the point of entrance of the bronchus into the lung. I have 

 mentioned several instances in the present communication. This 

 recess is enormously exaggerated in Heterodon platyrhinos, as 

 Pi-of. Cope (as well as others) has pointed out, and I can confirm 

 him from the examination of several individuals. It is in this 

 pocket of the lung that Prof. Cope seeks the origin of the tracheal 

 lung, if I rightly interpret the following passage, viz. (loc. cit. 

 p. 218) : — " The dorsal lung may present proximally alongside of 

 the trachea an auricle or pocket, and this is so developed in the 

 genus Heterodcm as to reach to the head, without communication 

 with the trachea, other than that furnished by the normal portion 

 of the lung. In the Solenoglypha, without exception, this ex- 

 tension of the dorsal lung is present, and extends to the head, and 

 its lumen is continuous with the trachea throughout its length. 

 The same structure exists," &c. In the above-given account of 

 various species of Ophidia, it will be seen that I have found the 

 pocket in question to coexist with the rudiments of a tracheal 

 lung independent of it. 



I cannot therefore accept Prof. Cope's view of the origin of the 

 tracheal lung, and I put forward my own suggestions in its place. 

 His attempt to classify Serpents by the character of the lungs will 

 possibly form the groundwork of a more successful scheme. At 

 present the facts are not sufficient for the elaboration of a com- 

 plete arrangement of those Reptiles. Cope is probably justified 

 in some of the details of the scheme, for example in the separation 

 of the genus JJngalia from other Boas and Pythons. It is clear, 

 however, that he is not necessarily right in separating Lepto- 

 gnathinse from Scytalinse, for though the former doubtless possess 

 a tracheal lung, I have shown that Erythrolamjyrus has considerable 

 traces of one. In details I have myself pointed out that the 

 characters of the lungs offer useful facts of assistance in classi- 

 fication. This is shown, for instance, among the species of the 

 genus Coluber, and the minute points of likeness between Erythro- 

 lamprus and another Opisthoglyph genus, viz. Tarhophis, are 

 noteworthy. The presence or absence of the rudimentary lung is 

 obviously not so useful a character. 



The usefulness of the lung-structure in settling details of 

 classification is also well shown in the case of Lioheterodon. This 

 genus was confused by earlier systematists with the American 

 Heterodon. Boulenger has shown *, utilising a structural pecu- 

 liarity in the dorsal vertebrse first made use of by Prof. Cope, 



* B. M. Cat. Snakes, vol. i. 1893, p. 171. 



