Common Ringed Snake. 29 



ceptions to be observed in the congeners of the subjects of com- 

 parison^ are to be noted, — the anchylosis of the iliac bones with the 

 neural spines of the anterior sacral vertebrae, the vertical rather 

 than horizontal direction of the external iliac fossae, and the 

 presence of praeacetabular spurs, of closed obturator tendinal fora- 

 mina, and of a more elongated sacro-ischiatic foramen. Internally, 

 the iliac fossae which are in relation with the upper lobe of the 

 kidney and the lower portion of the lung have one more vertebra 

 entering into their composition than the Pigeons ; and the middle 

 are less sharply limited off from the posterior renal fossae. 



The caudal vertebrae contrast with the rest of the column, with 

 the exception of the atlas, in being non-pneumatic ; and with all 

 the rest in the absence of well- developed articular facets on their 

 neural arches, and the connection of their centra, as in Mammalia 

 and crocodiles, by interarticular fibrocartilages. 



7. Common Einged Snake (Tropidonotus Natrix), 



Injected and dissected so as to show the way in which its various organs are arranged 

 within its cylindriform body, and especially how by their subordination to the 

 functions of prehension and deglutition of a living pi'ey, the digestive system 

 becomes the dominant system in the organization of these creatures. The dif- 

 ferent viscera have been exposed in situ by an incision carried along the middle 

 line of the ventral surface, and by the fastening out of the reflected integuments. 



The following peculiarities, most of which are explicable by a 

 reference to the special habits and needs of the creature, may be 

 first noted in a description of this preparation. Both the liver and 

 the pulmonary organs are unilobar, the left lung being merely 

 repi'esented by a rudimentary structure seen immediately to the 

 left of the apex of the heart ; the generative and the renal organs 

 are not arranged severally side by side, but each one of the right 

 side is placed more or less completely in front of its fellow of the left. 

 The oesophagus and stomach form together a highly distensible 

 tube running nearly directly from before backwards, whilst the 

 small intestine furnishes an example of a transversely folded di- 

 gestive tube arranged in short coils intimately connected with each 

 other. There is, however, no such approximation of the large 



