CIRCULATORY SYSTEM OF THE GRASS-SNAKE. 



617 



heart, which, however, in the course of the farther development 

 moves cauclally, and ultimately comes to lie a long way from its 

 primitive position. 



Text-fig. 87. 



PV.C. 



Dorsal view of the heart and adjoining vessels. 



C.V. Coronary vein. L.P.C. Left pre-caval vein (left common jugular). 

 E.P.C. Right pre-caval vein (right common jugular). S.V. Major part of sinus 

 venosus. S.V.I. Minor part of sinus venosus. Other letters as in text-fig. 86. 



(B) Adult Form. 



Tropidonotus in common with all the i-eptiles, except the 

 Orocodilia, possesses a three-chambered heart. This is situated a 

 considerable distance behind the head and slightly towards the 

 right. It is enclosed in a pericardium in which it lies freely, 

 not being attached to it by a gubernaculum cordis as is the case 

 in the heart of the Lacertilia and Orocodilia. Beddard (2) has 

 pointed out that although a gubernaculum cordis is generally 

 absent in snakes, it is not completely so, as a homologous structure 

 occurs in some species *. The pericardium on the right side lies 



* E. g. Coronella getula, Ccelopeltis monspessulana, and Ophiophagus hungarus, 

 Beddard {loc. cit.). 



Proc. Zool. Soc— 1912, No. XLI. 41 



