1906.] BESPIBATORY SYSTEMS IS" THE OPHID.IA. 521 



up, when adopting a threatening demeanour, to an unusual 

 extent. It will be observed that the tracheal lung of Coluher 

 corais is planned on the model of that of the "Viperidfe. But 

 instead of being vascular as in those Snakes, it is just the part of 

 the lung which is non-vascular, the vascularity commencing with 

 the thoracic lung. In the Vipers it is the tracheal lung which is 

 vascular and the thoracic lung which is not so, 



I am fortunately able to compare the state of affairs in this 

 species Coluber corais with that of other species of the genus 

 Coluher. These will now be dealt with. 



In Coluber longissimus {=C. cesculapii) there is also a tracheal 

 lung, which is, however, different in detail from that of C. corais. 

 The lung-tissue is, as usual, continuous with the dorsal mem- 

 branous interval between the tips of the incomplete tracheal rings. 

 This interval is narrow as in Serpents, with no tracheal lung ; but 

 for some distance, an inch or so, in front of the heart it has the 

 honeycombed structure of the lung proper. This fades away 

 gradually anteriorly into the ordinary membranous appearance 

 of this part of the respiratory apparatus in those Ophidia which 

 possess no tracheal lung. It does not seem to be vascular exce|')t 

 perhaps just at its commencement below, and has not the pink 

 colour characteristic of the functional lung. There is a rudi- 

 mentary second lung which is vascular as in Coluber corais, and 

 the existence of which has been duly noted by G. W. Butler*. 



Coluber ohsoletus {= alleghaniensis). — In a spirit-preserved 

 example of this Coluber there are also traces of the tracheal lung- 

 invading the membrane for some little distance in front of the 

 heart. There is also in this species a very distinct headwardly 

 directed caecum of the lung, as in other species of Coluber. There 

 is also present the second though rudimentary lung, which is, 

 however, cellular in structure and not a mere thin-walled sac. 

 The orifice into the second lung is exactly on a level with the 

 apex of the heart. The orifice has the form of a perforation of 

 the tracheal gutter. It does not lie in the lung- substance beside 

 it. The tracheal gutter is in this species fairly extensive. It can 

 be traced easily to a point lying about half an inch behind the 

 commencement of the liver, that is about 4 inches behind the 

 apex of the heart. Its termination coincides with the end of 

 the vascular region of the lung. The total length of the Snake 

 itself from mouth to vent is 47 inches. 



Coluber leojjardinus, though a small Snake like Coluber longissi- 

 mtts, has vestiges of the tracheal lung more like those of the large 

 Coluber corais. It resembles that species, in fact, by reason of the 

 grea,t width of the anangious membrane which divides the tracheal 

 rings at their tips anteriorly. The honeycomb structure of the 

 lung extends for a shorter distance than in Coluber longissimus in 

 front of the heart, and in this region the width of the " lung " is 

 less than anteriorly. Close to the apex of the heart — a little in 



* P. Z. S. 1895, p. 705. 



