191 6.] Fauna of the Chilka Lake : Mollusca Gastropoda, etc. 373 



The heart occupies the anterior half of the pericardial chamber, the ventricle 

 corresponding to the posterior end of the last intestinal loop in the visceral mass. 

 The ventricle is fusiform in shape. The two auricles are trapezoid in shape ; of the 

 two parallel sides, the shorter one is attached to the ventricle and the longer one to 

 the base of the gill. 



IX . Excretory System . 



Each kidney is (J-shaped with the loop placed posteriorly. The glandular portion, 

 lying beneath the pericardium, begins at a point behind the middle of the ventricle. 

 In the first part of its course the kidney is tubular and narrow and is placed on the 

 dorso-lateral aspects of the non-glandular portion and the visceral mass just above 

 the attachment of the gills. It then suddenly widens out into a bulbous portion, 

 pushing the gills downwards and outwards and lying on the outer side of the non- 

 glandular sac and on the dorso-lateral aspect of the hindermost portion of the visceral 

 mass and the ventro-lateral aspect of the rectum, both the two latter structures 

 being applied to the glandular sac. Anteriorly the bulbous portion is crescentic in 

 transverse section, the concave side being placed on the dorso-lateral aspect of the 

 hindermost part of the visceral mass and the cerebro- visceral nerve cord. Just be- 

 fore the formation of the posterior retractor muscle of the foot, the bulbous portion 

 widens out more on the inner aspect and communicates with the opposite one through 

 the inter-renal aperture. At this point the bulbous portion surrounds the rectum 

 on its ventral and lateral aspects. Gradually the inter-renal aperture widens out, 

 while the glandular sac surrounds the rectum more closely and completely. The 

 pericardial chamber is much narrowed down and flattened out, occupying the dorsal 

 aspect of the rectum. The glandular sac now recedes from the rectum and is dis- 

 placed ventral-wise by the interpolation of the two posterior retractor muscles which 

 lie by the side of the middle line, being separated by a median vertical partition 

 extending from below, where two glandular portions meet at their inner borders to the 

 side of the rectum above, to end in the mantle-lobe. L,astly the glandular portion 

 becomes narrowed down again and ends in the non-glandular portion by a small nar- 

 row slit. 



From the dorsal aspect of each of the two glandular sacs where they communi- 

 cate with one another at their ventral aspects, a diverticulum is given off, which 

 passes backwards for a short distance surrounding the ventral and lateral aspects of 

 the rectum, the dorsal aspect being occupied by the pericardial chamber. 



The non-glandular portion is very wide at its origin at the level of the visceral 

 ganglia, occupying the whole width between the attachments of the gills on either 

 side. It extends a little backwards beyond the posterior end of the glandular sac. 

 As it runs forwards, it occupies the outer side of the glandular sac and is gradually 

 displaced, at first to the ventral and lastly to the inner side of the glandular sac, 

 separated from each other at this place by a wide interval. The non-glandular sac 

 extends a little beyond the glandular sac at its anterior end. 



